List of shipwrecks from 1-15 April 1917

The list of shipwrecks in April 1917 includes some ships sunk, foundered, grounded, or otherwise lost during April 1917.

1 April

 * SS Aztec (1894) (🇺🇸 United States): World War I: The cargo ship was sunk in the Atlantic Ocean off Ouessant, Finistère, France (48.33333°N, -6°W) by SMU U-46 with the loss of 28 crew.
 * SS Bergenhus (1912) (🇩🇰 Denmark): World War I: The passenger ship was sunk in the North Sea 130 nmi east of the Farne Islands, Northumberland, United Kingdom by SMU UC-40 .There were no casualties.
 * SS Camilla (1908) (🇳🇴 Norway): World War I: The cargo ship was sunk in the North Sea 150 nmi west of Skudesnes, Rogaland (56.53333°N, 3.98333°W) by SMU UB-35 with the loss of eight of her crew.
 * SS Consul Persson (1890) (🇳🇴 Norway): World War I: The cargo ship was sunk in the North Sea (58.35°N, 2.91667°W) by SMU U-54 . Her crew survived.
 *  Eastern Belle ( undefined): World War I: The ketch was scuttled in the English Channel 30 nmi south west of St. Catherine's Point, Isle of Wight by SMU UC-72 . Her crew survived.
 * Endymion ( undefined): World War I: The ketch was shelled and sunk in the English Channel off Start Point, Devon by SMU UB-32 with the loss of four crew.
 * SS Ester (1917) (🇩🇰 Denmark): World War I: The cargo ship was sunk in the North Sea (56.53333°N, 4.3°W) by SMU UB-35 . Her crew survived.
 * SS Fjelland (1898) (🇳🇴 Norway): World War I: The coaster was sunk in the North Sea 50 nmi south west by west of Utsire, Rogaland (58.33333°N, 5.83333°W) by SMU U-54 with the loss of a crew member.
 * Jolie Brise (🇫🇷 France): World War I: The fishing vessel was sunk in the Atlantic Ocean 20 nmi off Audierne, Finistère by SMU UB-36.
 * SS Kasenga ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 2 nmi off Cape Palos, Spain by an enemy submarine.
 * Maria Santissima D. Grazie ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea off Sicily by SMU U-65 (Germany).
 * Maria T. ( undefined: World War I: The sailing vessel was sunk in the Mediterranean Sea off Sicily by SMU U-65 (Germany).
 * Providence de Dieu (🇫🇷 France): World War I: The fishing vessel was sunk in the Atlantic Ocean 20 nmi off Audierne by SMU UB-36.
 *  Silvia ( undefined): World War I: The schooner was scuttled in the English Channel 15 nmi south south east of the Owers Lightship ( undefined) (50.31667°N, -0.46667°W) by SMU UB-39 . Her crew survived.
 * SS Warren (1899) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Tyrrhenian Sea 20 nmi south west of Civitavecchia, Lazio, Italy (41.85°N, 11.36667°W) by SMU UC-38 with the loss of three of her crew. Her captain was taken as a prisoner of war.
 * SS Zambesi (1901) ( undefined): World War I: The collier was torpedoed and sunk in the Mediterranean Sea 15 nmi north by west of Alexandria, Egypt (31.43333°N, 29.81667°W) by SMU U-63 (Germany) with the loss of three crew.

2 April

 * SS Britannia (1885) ( undefined): World War I: The cargo ship torpedoed and was sunk in the Mediterranean Sea 22 nmi west north west of Pantelleria, Italy (36.58333°N, 11.46667°W) by SMU U-65 (Germany) . Her crew survived, but two of them were taken as prisoners of war.
 * HMT Commandant : World War I: The naval trawler struck a mine and sank in the North Sea off the Sunk Lightship ( undefined) (51.55°N, 1.6°W) with the loss of five of her crew.
 * ST Filicudi : World War I: The naval tug struck a mine and sank in the Mediterranean Sea off Trapani, Sicily.
 * SS Havlyst (1895) (🇳🇴 Norway): World War I: The coaster was sunk in the North Sea off Lindesnes, Vest-Agder (57.5°N, 6.83333°W) by SMU U-54 . Her crew survived.
 * Lord Scarborough ( undefined): World War I: The trawler was sunk in the North Sea 100 nmi east of the Isle of May, Fife by SMU UB-35 . Her crew survived.
 *  Saggita (🇳🇴 Norway): World War I: The barque was sunk in the North Sea (60°N, -2°W) by SMU U-78 . Her crew survived.
 *  Snespurven (🇳🇴 Norway): World War I: The barque was shelled and sunk in the Atlantic Ocean 25 nmi south south west of the Tuskar Rock, Ireland (50.91667°N, -7.05°W) by SMU U-59 . Her crew survived.
 * SS Zealandia (1875) (🇺🇸 United States) The ship ran aground off Southport, Lancashire, United Kingdom.

3 April

 *  Annunziata A. ( undefined): World War I: The brigantine was scuttled in the Mediterranean Sea east of Sardinia (39.86667°N, 10.06667°W) by SMU UC-38.
 * SS Ardgask (1917) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 15 nmi south west of Cape Rosello, Sicily by SMU U-35 (Germany) with the loss of a crew member.
 *  Caterina R. ( undefined): World War I: The barquentine was scuttled in the Mediterranean Sea east of Sicily (39.45°N, 9.76667°W) by SMU UC-38.
 * Domenico ( undefined): World War I: The sailing vessel was scuttled in the Mediterranean Sea east of Sardinia (39.4°N, 9.91667°W) by SMU UC-38.
 *  Ellen James ( undefined): World War I: The schooner was shelled and sunk in the Atlantic Ocean west of Ouessant, Finistère, France by SMU UC-71 with the loss of five of her crew.
 * SS Ernest Simons (1893) (🇫🇷 France): World War I: The passenger ship was sunk in the Mediterranean Sea north east of Cap Sera, Algeria (37.13333°N, 8.46667°W) by SMU UC-37 . Her crew survived.
 * SS Hesperus (1903) ( undefined): World War I: The cargo ship was sunk in the Atlantic Ocean 72 nmi off the Bishop Rock, Isles of Scilly, United Kingdom (48.83333°N, -7.33333°W) by SMU U-46 . Her crew survived.
 * Maria Ferrara ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea west of Sicily by SMU U-65 (Germany).
 * Nuova Maria di Porto Salvo ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea east of Sicily by SMU UC-38.
 * SS Saint Simon (1912) (🇫🇷 France): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 20 nmi north west of La Galite, Tunisia (37.6°N, 8.63333°W) by SMU UC-37.
 * SS Vasilefs Constantinos (1913) (🇬🇷 Greece): World War I: The cargo ship was sunk in the Aegean Sea 45 nmi south west of Akra Akritas by SMU UB-43.

4 April

 * SS City of Paris (1907) ( undefined): World War I: The passenger ship was torpedoed and sunk in the Mediterranean Sea 46 nmi south by east of Cap d'Antibes, Alpes-Maritimes, France (42.9°N, 7.63333°W) by SMU UC-35 with the loss of 122 lives.
 * SS Domingo (1881) ( undefined): World War I: The cargo ship was sunk in the Atlantic Ocean off Queenstown, County Cork, United Kingdom by SMU U-60.
 * Gibraltar ( undefined): World War I: The trawler was scuttled in the North Sea 20 nmi east north east of Rattray Head, Aberdeenshire by SMU UB-35 . Her crew survived.
 * SS Hundvaagø (1915) (🇳🇴 Norway): World War I: The cargo ship was torpedoed and damaged in the Atlantic Ocean south west of Ireland. She was beached at Castletownbere, County Cork. Subsequently repaired and returned to service.
 * SS Hunstanton (1903) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 36 nmi west of the Isles of Scilly (49.83333°N, -7.66667°W) by SMU UC-30 . Her crew survived.
 * Maggie Ross ( undefined): World War I: The trawler was shelled and sunk in the North Sea 60 nmi north east of Girdle Ness, Aberdeenshire by SMU UB-35 . Her crew survived.
 * SS Margit (1903) ( undefined): World War I: The collier was torpedoed and sunk in the Mediterranean Sea 80 nmi south west of Cape Matapan, Greece (35.46667°N, 21.4°W) by SMU U-63 (Germany) . Her crew survived.
 *  Marguerite (🇺🇸 United States): World War I: The four-masted schooner was damaged in the Mediterranean Sea 35 nmi south west of Sardinia by SMU U-35 (Germany) . She sank the next day; her crew survived.
 * SS Missourian (1903) (🇺🇸 United States): World War I: The cargo ship was sunk in the Tyrrhenian Sea off Porto Maurizio, Liguria, Italy by SMU U-52 . Her crew survived.
 *  Monte Protedigo (🇦🇷 Argentina): World War I: The barquentine was sunk in the Atlantic Ocean off the Isles of Scilly (49.45°N, -6.73333°W) by SMU UC-30.
 * SS Parana (1893) (🇧🇷 Brazil): World War I: The cargo ship was sunk in the English Channel off Barfleur, Manche, France by SMU UB-32 . Her crew survived.
 * SS Parkgate (1906) ( undefined): World War I: The cargo ship was scuttled in the Mediterranean Sea 80 nmi north east of the Cap de Fer, Algeria (38.2°N, 8.16667°W) by SMU U-35 (Germany) with the loss of sixteen crew. Her captain was taken as a prisoner of war.
 * SS Penseiro (1888) ( undefined): World War I: The cargo ship was scuttled in the Atlantic Ocean 40 nmi west of the Isles of Scilly by SMU UC-71 . Her crew survived.
 * SS Ravenna (1901) ( undefined): World War I: The passenger ship was sunk in the Tyrhhenian Sea 2 nmi off Cape Mele, Liguria (44°N, 8.46667°W) by SMU U-52.
 * San Giovanni Battiste ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea by SMU UC-37.
 * SS Trevier (1907) (🇧🇪 Belgium) World War I: The cargo ship was torpedoed, shelled and sunk in the North Sea off Scheveningen, South Holland, Netherlands (52.25°N, 3.81667°W) by SM UB-23.
 * SS Vladimir Reitz (1905) (🇩🇰 Denmark): World War I: The cargo ship was sunk in the Atlantic Ocean 40 nmi north west by north of Foula, Shetland Islands, United Kingdom by SMU U-78 with the loss of two crew.

5 April

 *  Amiral L'Hermite (🇫🇷 France): World War I: The schooner was scuttled in the Atlantic Ocean 60 nmi west north west of the Blasket Islands, County Kerry, United Kingdom by SMU U-59.
 * Angel Marina ( undefined): World War I: The sailing vessel was scuttled in the Ligurian Sea (43.26667°N, 7.16667°W) by SMU U-52.
 * SS Benheather (1913) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 110 nmi west north west of the Fastnet Rock (51.33333°N, -12.5°W) by SMU U-46 . Her crew survived.
 *  Bris (🇩🇰 Denmark): World War I: The schooner was sunk in the Atlantic Ocean 20 nmi north of the Butt of Lewis, Outer Hebrides, United Kingdom by SMU U-78 with the loss of two of her crew.
 * SS Calliope (1901) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Tyrrhenian Sea 35 nmi south west of Ustica, Italy (38.36667°N, 11.41667°W) by SMU U-65 (Germany) with the loss of six lives. Three survivors were taken as prisoners of war.
 * SS Canadian (1900) ( undefined): World War I: The passenger ship was torpedoed and sunk in the Atlantic Ocean 47 nmi north west of the Fastnet Rock (51.6°N, -10.8°W) by SMU U-59 with the loss of a crew member.
 * SS Dicto (1904) (🇳🇴 Norway): World War I: The cargo ship was sunk in the Atlantic Ocean south east of the Armen Rock by SMU UB-39 with the loss of a crew member.
 *  Dunkerquois (🇫🇷 France): World War I: The schooner was sunk in the Atlantic Ocean 45 nmi off the Blasket Islands by SMU U-86.
 *  Ebenezer (🇩🇰 Denmark): World War I: The three-masted schooner was shelled and sunk in the Atlantic Ocean 10 nmi south west of St. Kilda, United Kingdom (57.96667°N, -8.33333°W) by SMU U-57 . Her crew survived.
 *  Ernest Legouve (🇫🇷 France): World War I: The barque was torpedoed and sunk in the English Channel 5 nmi west by south of St. Catherine's Point, Isle of Wight, United Kingdom (50.5°N, -1.43333°W) by SMU UB-32 with the loss of twenty of her 24 crew.
 * SS Gower Coast (1899) ( undefined): World War I: The coaster struck a mine and sank in the English Channel off Le Tréport, Seine-Maritime, France with the loss of all fifteen crew.
 *  Marie Celine (🇫🇷 France): World War I: The schooner was sunk in the Atlantic Ocean south west of Ireland by SMU U-86.
 * SS N. J. Fjord (1896) (🇩🇰 Denmark): World War I: The cargo ship was scuttled in the North Sea 40 nmi east north east of Coquet Island, Northumberland, United Kingdom. Her crew survived.
 * Roland (🇫🇷 France): World War I: The sailing vessel was sunk in the Atlantic Ocean 80 nmi west north west of the Blasket Islands by SMU U-59.
 * SS San Fulgencio (1901) (🇪🇸 Spain): World War I: Teh cargo ship was sunk in the Bay of Biscay off Sables d'Olonne, Vendée, France by SMU UC-71.
 * SS Siberier (🇧🇪 Belgium) World War I: The cargo ship was torpedoed and damaged in the Atlantic Ocean 40 nmi west of the Fastnet Rock (52.3°N, -11.66667°W) by SMU U-86 . She was taken in tow but sank the next day.
 * SS Solstad (1916) (🇳🇴 Norway): World War I: The cargo ship was sunk in the Ionian Sea north west of Cythera, Greece (36.03333°N, 20.83333°W) by SMU U-63 (Germany) . Her crew survived.
 * SS Vilja (1915) (🇳🇴 Norway): World War I: The cargo ship was torpedoed and sunk in the Atlantic OCean 135 nmi west of the Fastnet Rock (52.2°N, -13.11667°W) by SMU U-55 with the loss of a crew member.

6 April

 * Cybele (🇫🇷 France): World War I: The sailing vessel was sunk in the Mediterranean Sea of Cabo de Gata, Almeria, Spain by SMU UC-25.
 * SS Kongshaug (1884) (🇳🇴 Norway): World War I: The coaster was captured and scuttled in the North Sea 45 nmi north of Kinnaird Head, Aberdeenshire, United Kingdom by SM UB-35 . Her crew were rescued by a Scottish fishing vessel.
 *  La Tour d'Auvergne (🇫🇷 France): World War I: The brig was shelled and set on fire in the Atlantic Ocean 15 nmi south south east of the Longships Lighthouse by SMU UB-39 . She was towed to Mullion, Cornwall, United Kingdom but was declared a constructive total loss. Her crew survived.
 * Lord Kitchener ( undefined): World War I: The trawler was scuttled in the North Sea 45 nmi north by east of Kinnaird Head by SMU UB-35 . Her crew survived.
 *  Marion (🇳🇴 Norway): World War I: The barque was shelled and sunk in the Atlantic Ocean (52.16667°N, -13.76667°W) by SMU U-60 with the loss of a crew member.
 * Narberth Castle ( undefined): World War I: The trawler was shelled and sunk in the North Sea 30 nmi north north west of Dennis Head Old Beacon, North Ronaldsay, Orkney Islands by SMU UC-27 . Her crew survived.
 * Nestor ( undefined): World War I: The trawler was shelled and sunk in the North Sea 20 nmi north west by north of North Ronaldsay by SMU UC-27 . Her crew survived.
 *  Perce Neige (🇫🇷 France): World War I: The schooner was sunk in the Atlantic Ocean off Lands End, Cornwall, United Kingdom by SMU UB-39.
 * SS Powhatan (1898) ( undefined): World War I: The tanker was torpedoed and sunk in the Atlantic Ocean 25 nmi north by west of North Rona (59.53333°N, -6.5°W) by SMU U-66 with the loss of 36 crew. Her captain was taken as a prisoner of war.
 * SS Presto (1905) ( undefined): World War I: The cargo ship struck a mine and sank in the North Sea 4 nmi east of Roker Point, Sunderland, County Durham (54.95°N, -1.26667°W) with the loss of six of her crew.
 * Rahmanich (🇪🇬 Egypt): World War I: The ship was sunk in the Mediterranean Sea off the coast of Egypt by SMU UC-34.
 * Recto ( undefined): World War I: The trawler was scuttled in the North Sea 45 nmi north by east of Kinnaird Head by SMU UB-35 . Her crew survived.
 * SS Rosalind (1913) ( undefined): World War I: The tanker was torpedoed and sunk in the Atlantic Ocean 180 nmi west north west of the Fastnet Rock (51.65°N, -14.33333°W) by SMU U-86 with the loss of two of her crew.
 * SS Spithead (1899) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 12 nmi north by west of the Damietta Lighthouse, Egypt (31.73333°N, 31.76667°W) by SMU UC-34 with the loss of a crew member.
 * HMT Strathrannoch : World War I: The naval trawler struck a mine and sank in the North Sea off St. Abb's Head, Berwickshire (55.91667°N, -2.11667°W) with the loss of all thirteen crew.
 * SS Thelma (1884) (🇳🇴 Norway): World War I: The cargo ship struck a mine and sank in the English Channel 4 nmi south by west of the Owers Lightship ( undefined) by SMU UC-65 with the loss of a crew member.
 * SS Vine Branch (1896) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean south west of Ireland (49.75°N, -14.13333°W) by SMU U-55 with the loss of all 44 crew.

7 April

 * SS Caminha (1907) (🇵🇹 Portugal) World War I: The cargo ship was sunk in the Bay of Biscay 30 nmi south south west of Cape Ferrat (45.36667°N, -2.8°W) by gunfire from SM UC-71.
 * SMS Cormoran (1909) : World War I: The merchant raider was scuttled at Guam with the loss of nine crew.
 *  Edwin R. Hunt (🇺🇸 United States): World War I: The schooner was sunk in the Mediterranean Sea 40 nmi off Cabo de Gata, Almeria, Spain by SMU UC-25 . Her crew survived.
 *  Fiskaa (🇳🇴 Norway): World War I: The barque was sunk in the Atlantic Ocean 10 nmi off St. Kilda, United Kingdom by SMU U-46 . Her crew survived.
 * HMS Jason (1892) : World War I: The minesweeper struck a mine and sank off Coll, Inner Hebrides (56.59583°N, -6.47083°W) with the loss of 25 crew.
 * SS Lapland ( undefined) World War I: The passenger ship struck a mine off the Liverpool Bar Lightship ( undefined) and was damaged. She was later repaired and returned to service.
 * SS Maplewood (1915) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 47 nmi south west of Cape Sperone, Sardinia, Italy by SMU U-35 (Germany) . Her crew survived.
 * SS Salmo (1900) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 210 nmi north west of the Fastnet Rock (52.5°N, -14.66667°W) by SMU U-60 with the loss of two crew.
 * SS Seward (1907) (🇺🇸 United States): World War I: The cargo ship was shelled and sunk in the Mediterranean Sea 22 nmi north east of Begur, Spain (42.7°N, 3.68333°W) by SMU U-52 . Her crew survived.
 * SS Trefusis (1893) ( undefined): World War I: The collier was scuttled in the Mediterranean Sea 30 nmi south east of Cape Pula, Sardinia (38.63333°N, 9.41667°W) by SMU U-65 (Germany) . Her crew survived, but three survivors were taken as prisoners of war.

8 April

 * SS Alba (1881) ( undefined): World War I: The cargo ship was sunk in the Mediterranean Sea 3 nmi off Garraf, Catalonia, Spain (41.08333°N, 1.88333°W) by SMU U-52.
 * SMS G88 : World War I: The V25-class destroyer was torpedoed and sunk in the North Sea by a Royal Navy Coastal Motor Boat.
 * Geilan Bahri ( undefined): World War I: The sailing vessel was scuttled in the Mediterranean Sea 54 nmi off Alexandria, Egypt by SMU UC-34.
 * SS Livatho (1891) (🇬🇷 Greece): World War I: The cargo ship was sunk in the Mediterranean Sea north west of Crete (36.4°N, 20.93333°W) by SMU UB-47 . Her crew survived.
 * Lucia ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea off Cape Pula, Sardinia by SMU U-65 (Germany).
 * SS Nestos (1914) (🇬🇷 Greece): World War I: The cargo ship was sunk in the Mediterranean Sea 50 nmi west south west of Sapientza (36.45°N, 20.98333°W) by SMU UB-47.
 * Papa Gian Battista ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea off Cape Pula, Sardinia by SMU U-65 (Germany).
 * SS Petridge (1913) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 200 nmi west north west of Ouessant, Finistère, France (48.23333°N, -10.16667°W) by SMU U-55 . Her crew survived, but two of them were taken as prisoners of war.
 * SS Torrington (1905) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic OCean 150 nmi south west of the Isles of Scilly by SMU U-55 with the loss of 34 crew. Her captain was taken as a prisoner of war.
 * SS Umvoti (1896) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic OCean 200 nmi west north west of Ouessant (48.8°N, -10.25°W) by SMU U-55 with the loss of four crew. Two survivors were taken as prisoners of war.

9 April

 * SS Avon (1894) ( undefined): World War I: The passenger ship struck a mine and sank in the Thames Estuary 2.5 nmi south east by south of the Tongue Lightship ( undefined) (51.48333°N, 1.44167°W) with the loss of two lives.
 * SS Cairnie ( undefined): The coaster dragged her anchors, collided with another vessel and sank. Her crew were rescued.
 * SS Esterel (1904) (🇫🇷 France): World War I: The cargo shipb was sunk in the Mediterranean Sea off Port-Vendres, Pyrénées-Orientales (42.65°N, 3.5°W) by SMU U-52.
 *  Fremad I: 🇳🇴 Norway): World War I: The barque was sunk in the North Sea 200 nmi off Lindesnes, Vest-Agder (58.78333°N, 0.86667°W) by SMU U-59 . Her crew survived.
 * SS Ganslei (1904) ( undefined): World War I: The cargo ship was sunk in Kola Bay (69.31667°N, 33.51667°W) by SMU U-75.
 * SS Kittiwake (1906) ( undefined): World War I: The cargo ship was torpedoed and sunk in the North Sea 25 nmi north west of the Maas Lightship (🇳🇱 Netherlands) (52.25°N, 3.3°W) by SMU UB-30 with the loss of seven crew.
 * HMT Ortho : World War I: The naval trawler struck a mine and sank in the North Sea off Lowestoft, Suffolk (52.38333°N, 1.875°W) with the loss of a crew member.
 * Saint Maudez (🇫🇷 France): World War I: The sailing vessel was sunk in the English Channel 10 nmi north north west of Fécamp, Seine-Maritime by SMU UB-39.
 * SS Themistoclis (1880) (🇬🇷 Greece): World War I: The cargo ship was sunk in the Atlantic Ocean 100 nmi off Pointe Saint-Mathieu, Finistère, France by SMU UC-71.
 * SS Valhall (1902) (🇳🇴 Norway): World War I: The cargo ship was sunk in the Atlantic Ocean 30 nmi north of the Pierres Noires, Finistère by SMU UC-71 . Her crew survived.

10 April

 * Abd Razid (Flag of French Tunisia.svg Tunisia): World War I: The sailing vessel was sunk in the Mediterranean Sea off Tripoli, Libya by SMU UC-20.
 * SS Dalton (1904) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea off Cape Matapan, Greece (36°N, 22.66667°W) by SMU U-28 (Austria-Hungary) . Her crew survived.
 * HMS P26 : World War I: The P-class sloop struck a mine and sank in the English Channel off Le Havre, Seine-Maritime, France with the loss of nineteen of her 59crew. Survivors were rescued by HMS P19 (
 * SS Pluto (1897) ( undefined): World War I: The cargo ship was torpedoed and sunk in the North Sea 32 nmi south east by east of Lowestoft, Suffolk (52.31667°N, 2.56667°W) by SMU UB-20 . Her crew survived.
 * SS Porto di Rodi (1897) ( undefined: World War I: The cargo ship was sunk in the Ionian Sea 37.88333°N, 18.03333°W) SMU U-32 (Germany) with the loss of 31 crew.
 * SS Ranvik (1911) (🇳🇴 Norway): World War I: The cargo ship was sunk in the Atlantic Ocean 45 nmi west south west of Ouessant, Finistère, France by SMU UC-71 . Her crew survived.
 *  : World War I: The hospital ship struck a mine and sank at Le Havre with the loss of 130 of the 205 people on board.

11 April

 * HMT Amy : World War I: The naval trawler struck a mine and sank in the English Channel off Le Havre, Seine Maritime, France with the loss of nine of her crew.
 *  Ansgar (🇩🇰 Denmark): World War I: The barquentine was set afire and sunk in the Mediterranean Sea off Cape San Antonio, Spain (39.1°N, 0.5°W) by SMU U-52 . Her crew survived.
 * SS Candia (1862) ( undefined): World War I: The cargo ship was sunk in the Mediterranean Sea off Zuwara, Libya by SMU UC-20.
 * SS Cyfarthfa (1904) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 32 nmi west south west of Antikythera, Greece (35.48333°N, 22.5°W) by SMU UB-47 . Her crew survived.
 * SS Duchess of Cornwall (1889) ( undefined): World War I: The cargo ship struck a mine and sank in the English Channel 5 nmi north of Cape Barfleur, Manche, France with the loss of 23 of her crew.
 * SS Imperial Transport (1913) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 140 nmi north west by north of Alexandria, Egypt by SMU UC-34 . Her crew survived, but her captain was taken as a prisoner of war.
 *  Miss Morris ( undefined): World War I: The three-masted schooner was scuttled in the Mediterranean Sea 20 nmi south east of Garrucha, Andalusia, Spain (36.95°N, -1.83333°W) by SMU U-35 (Germany) . Her crew survived.
 * SS Nancy (1888) (🇩🇰 Denmark): World War I: The cargo ship was torpedoed and sunk in the North Sea 42 nmi off the Hellisøy Lighthouse, Hordaland, Norway by SMU U-30 (Germany) with the loss of three crew.
 * Precedent ( undefined): World War I: The fishing smack was scuttled in the English Channel 12 nmi east south east of Berry Head, Devon by SMU UB-38 . Her crew survived.
 * SS Quaggy (1904) ( undefined): World War I: The coaster struck a mine and sank in the North Sea 3 nmi east of Robin Hood's Bay, Yorkshire with the loss of two of her crew.
 *  Sarvsfos (🇳🇴 Norway): World War I: The barque was sunk in the North Sea 80 nmi south east of Kirkwall, Orkney Islands (58.55°N, °W) by SMU U-50 . Her crew survived.
 * SS Saxo (1907) (🇩🇰 Denmark: World War I: The coaster was sunk in the North Sea 42 nmi off the Hellisøy Lighthouse by SMU U-30 (Germany) . Her crew survived.
 * SS Star (1907) (🇳🇴 Norway): World War I: The coaster was sunk in the North Sea 68 nmi off the coast of Fife, United Kingdom by SMU U-30 (Germany) . Her crew survived.
 *  Sylfiden (🇳🇴 Norway): World War I: The barque was sunk in the Barents Sea 50 nmi north by west of Holmengrå, Finnmark by SMU U-30 (Germany) . Her crew survived.
 * SS Tremorvah (1905) ( undefined): World War I: The cargo ship was shelled and sunk in the Mediterranean Sea 70 nmi north north west of Cape Bougaroni, Algeria by SMU U-65 (Germany) . Her crew survived, but four of them were taken as prisoners of war.

12 April

 *  Angela M. ( undefined): World War I: The three-masted schooner was scuttled in the Mediterranean Sea north west of Cape Bougaroni, Algeria by SMU U-65 (Germany).
 * Caliban ( undefined): World War I: The trawler was shelled and sunk in the North Sea 45 nmi north east by east of Rattray Head, Aberdeenshire by SMU UC-76 . Her crew survived.
 * Chinkiang ( undefined): World War I: The trawler was shelled and sunk in the North Sea 30 nmi north east by east of Buchan Ness, Aberdeenshire by SMU UC-76 . Her crew survived.
 * Crown Prince ( undefined): World War I: The trawler was shelled and sunk in the North Sea 45 nmi north east by east of Girdle Ness by SMU UC-76 . Her crew survived.
 * Dina Henderika (🇳🇱 Netherlands): World War I: The sailing vessel was scuttled in the North Sea 30 nmi east north east of Hartlepool, County Durham, United Kingdom by SMU UC-30.
 * Edelweiss (🇫🇷 France): World War I: The sailing vessel was shelled and sunk in the English Channel off Cherbourg, Seine-Maritime by SMU UC-71.
 * Equerry ( undefined): World War I: The trawler was shelled and sunk in the North Sea 35 nmi north east of Kincaid Head by SMU UC-76 . Her crew survived.
 * Ernst Sophie ( undefined): World War I: The sailing vessel was scuttled in the Atlantic Ocean south west of Ireland (51.08333°N, -11.96667°W) by SMU UC-27.
 * Fife Ness ( undefined): World War I: The fishing vessel was shelled and sunk in the North Sea 23 nmi east north east of Fraserburgh, Aberdeenshire by SMU UC-76 . Her crew survived.
 * SS Glencliffe (1910) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 2.5 nmi off Tabarka Island, Alicante, Spain (38.11667°N, -0.36667°W) by SMU U-52 with the loss of a crew member. Three survivors were taken as prisoners of war.
 * SS India (1899) (🇬🇷 Greece): World War I: The cargo ship was sunk in the Mediterranean Sea east of Gibraltar by SMU U-35 (Germany).
 * SS Kildale (1906) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 40 nmi east of Pantelleria, Italy (36.73333°N, 12.53333°W) SMU U-32 (Germany) with the loss of a crew member.
 * SS Kolaastind (🇳🇴 Norway): World War I: The cargo ship was sunk in the North Sea (60.23333°N, 2.7°W) by SMU U-30 (Germany) with the loss of four crew.
 * Largo Bay ( undefined): World War I: The trawler was shelled and sunk in the North Sea 30 nmi north east by east of Buchan Ness by SMU UC-76 . Her crew survived.
 * Lilian ( undefined): World War I: The trawler was shelled and sunk in the North Sea 45 nmi north east by east of Girdle Ness by SMU UC-76 . Her crew survived.
 * SS Lismore (1905) ( undefined): World War I: The passenger ship was torpedoed and sunk in the English Channel 22 nmi north west by north of Le Havre, Seine-Maritime, France (49.8°N, -0.3°W) by SMU UB-38 with the loss of five lives.
 * Neptunus (🇳🇱 Netherlands): World War I: The sailing vessel was sunk in the North Sea 20 nmi east north east of Hartlepool by SMU UC-30.
 * SS Niritos (1906) (🇬🇷 Greece): World War I: The cargo ship was sunk in the Mediterranean Sea 5 nmi off Augusta, Sicily, Italy (37.21667°N, 15.33333°W) by SMU U-27 (Austria-Hungary).
 * Osprey ( undefined): World War I: The trawler was shelled and sunk in the North Sea 45 nmi north east by east of Girdle Ness by SMU UC-76 . Her crew survived.
 * SS Toro (1904) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 200 nmi west north west of Ouessant, Finistère, France (48.5°N, -10°W) by SMU U-55 with the loss of fourteen crew. Two survivors were taken as prisoners of war.
 *  Union (🇩🇰 Denmark): World War I: The schooner was sunk in the North Sea 18 to 20 nmi east of the Souter Lighthouse, County Durham by SMU UC-30 . Her crew survived.
 *  Voorwarts (🇳🇱 Netherlands): World War I: The schooner was sunk in the North Sea 20 nmi east north east of Hartlepool by SMU UC-30.

13 April

 * SS Argyll (1901) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 110 nmi west of the Bishop Rock, Isles of Scilly (49.38333°N, -9.11667°W) by SMU U-84 with the loss of 22 of her crew.
 * SS Bandon (1910) ( undefined): World War I: The cargo ship struck a mine and sank in the Atlantic Ocean 2.5 nmi south west of Mine Head, Cornwall (51.95°N, -7.58333°W) with the loss of 28 of her crew.
 * SS Bokn (1901) (🇳🇴 Norway): World War I: The coaster was sunk in the North Sea 95 nmi off the Hellisøy Lighthouse, Hordaland (60.06667°N, 0.75°W) by SMU U-30 (Germany) . Her crew survived.
 * SS Frixos (1888) ( undefined): World War I: The cargo ship was torpedoed and sunk in the North Sea 60 nmi east of the Shetland Islands, United Kingdom (60.06667°N, 0.75°W) by SMU U-30 (Germany).
 * SS Gama (1910) (🇳🇴 Norway): World War I: The coaster was sunk in the North Sea (60.4°N, 1.25°W) by SMU U-30 (Germany) . Her crew survived.
 * Gambetta (🇫🇷 France): The sailing vessel was sunk in the Bay of Biscay off the Île d'Yeu, Finistère by SMU UC-26.
 * SS Giuseppe Accame (1899) ( undefined): World War I: The cargo ship was sunk in the Mediterranean Sea 40 nmi west of Cape Spartel, Morocco by SMU U-35 (Germany).
 *  Glenlora (🇳🇴 Norway): World War I: The barque was sunk in the North Sea (60.6°N, 1.88333°W) by SMU U-30 (Germany) . Her crew survived.
 * SS Kariba (1904) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 260 nmi west nort west of Ouessant, Finistère, France (48.5°N, -11.46667°W) by SMU UC-27 with the loss of thirteen of her crew.
 *  Maria ( undefined): World War I: The schooner was scuttled in the English Channel 25 nmi south west of Portland Bill, Dorset by SMU UB-38 . Her crew survived.
 * HMML 534 : World War I: The motor launch was lost in the Mediterranean Sea on this date.
 * SS Odysseus (4531) (🇬🇷 Greece): World War I: The cargo ship was sunk in the Mediterranean Sea 30 nmi west of Cape Spartel by SMU U-35 (Germany).
 * HMT Pitstruan : World War I: The naval trawler struck a mine and sank in the North Sea 3 nmi south east of the Noss Head Lighthouse, Shetland Islands with the loss of eleven of her crew.
 * Stork ( undefined): World War I: The trawler was scuttled in the North Sea 20 nmi east of St Abb's Head, Berwickshire by SMU UC-41 . Her crew survived.
 * SS Strathcona (1900) (🇨🇦 Canada): World War I: The cargo ship was scuttled in the Atlantic Ocean 145 nmi west north west of Ronaldsay, Orkney Islands, United Kingdom (59.58333°N, -5.81667°W) by SMU U-78 with the loss of nine crew. Three survivors were taken as prisoners of war.
 * SS Stromboli (1914) ( undefined): The cargo ship was sunk in the Mediterranean Sea 50 nmi west of Cape Spartel by SMU U-35 (Germany).
 * SS Zara (1897) ( undefined): World War I: The cargo ship was torpedoed and sunk in the North Sea 90 nmi off the Hellisøy Lighthouse (60.13333°N, 1.86667°W) by SMU U-30 (Germany) with the loss of 27 lives.

14 April

 * HMT Alberta : World War I: The naval trawler struck a mine and sank in the North Sea off Grimsby, Lincolnshire (53.75°N, 0.85°W) with the loss of seven of her crew.
 * Andromach ( undefined): World War I: The trawler was scuttled in the Atlantic Ocean west of the Shetland Islands by SMU U-78 . Her captain was taken as a prisoner of war. The other eleven crew took to the lifeboat but were not found.
 * Cinque Ottobre ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea off the coast of Tunisia by SMU UC-20.
 * SS Fjeldli (🇳🇴 Norway): World War I: The coaster was sunk in the North Sea 76 nmi west by north of the Marstein Lighthouse, Hordaland (60.03333°N, 2.16667°W) by SMU U-30 (Germany) . Her crew survived.
 * SS Gange (1905) : World War I: The troopship struck a mine and sank in the Mediterranean Sea 33 nmi north east of Cape Serrat, Algeria (37.4°N, 9.83333°W) by SMU UC-37 with the loss of one life.
 * SS Hermione (1891) ( undefined): World War I: The cargo ship struck a mine and was damaged in the Irish Sea off the Coningbeg Lightship ( undefined). She was beached in Dunmore Bay where she was declared a constructive total loss. Subsequently scrapped in situ.
 * HMT Orcades : World War I: The naval trawler struck a mine and sank in the North Sea off Grimsby with the loss of six of her crew.
 * SS Patagonier (1910) ( undefined): World War I: The cargo ship was shelled and sunk in the Mediterranean Sea 135 nmi) west of Gibraltar (36°N, -9°W) by SMU U-35 (Germany) . Her crew survived.
 * ST Progresso ( undefined): World War I: The tug was sunk in the Mediterranean Sea off the coast of Tunisia by SMU UC-20.
 * SS Spray (1891) ( undefined): World War I: The cargo ship was sunk in the North Sea 3.5 nmi north east of the mouth of the River Tyne by SMU UC-30 . Her crew survived.
 * SS Tom (1896) (🇪🇸 Spain): World War I: The cargo ship was sunk in the Bay of Biscay 12 nmi off Hourtin, Gironde, France (45.08333°N, -1.5°W) by SMU UC-26 . Her crew survived.
 * Tres Macs (🇵🇹 Portugal): World War I: The auxiliary sailing vessel was shelled and sunk in the Mediterranean Sea (36.65°N, -7.36667°W) by SMU U-52.
 * SS Venus (1872) (🇳🇴 Norway): World War I: The coaster struck a mine and sank in the North Sea 5 nmi off Berwick-upon-Tweed, Northumberland, United Kingdom with the loss of fourteen of her crew.
 * HMS Veronica (1915) The Acacia-class sloop was damaged in the Mediterranean Sea 45 nmi north west of Alexandria, Egypt (31.71667°N, 29.28333°W) by SMU UB-42.

15 April

 * SS Alert (1911) ( undefined): World War I: The coaster struck a mine and sank in the English Channel off Dover, Kent.
 * Alessio Cocco ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea off the coast of Tunisia by SMU UC-20.
 * SS Arcadian (1899) ( undefined): World War I: The troopship was torpedoed and sunk in the Mediterranean Sea 26 nmi north east of Milos, Greece (36.83333°N, 24.83333°W) by SMU UC-74 with the loss of 277 lives.
 *  Astræa (🇩🇰 Denmark): World War I: The barquentine was set afire and sunk in the Atlantic Ocean south west of the Isles of Scilly, United Kingdom (49°N, -10.5°W) by SMU U-55 with the loss of seven crew.
 * Brothertoft ( undefined): World War I: The trawler was sunk in the North Sea (approximately 55.83333°N, 1.5°W) by SMU UC-30.
 * SS Cameronia (1911) ( undefined): World War I: The troopship was torpedoed and sunk in the Mediterranean Sea 150 nmi east of Malta (35.83333°N, 17.53333°W) by SMU U-33 with the loss of 140-210 of the 2,650-plus people on board. Survivors were rescued by HMS Nemesis (1910) and HMS Rifleman (1910) (both ).
 * Dalmatian ( undefined): World War I: The trawler was scuttled in the North Sea by SMU UC-44 . Her nine crew took to the lifeboats but did not survive.
 *  Fram (🇩🇰 Denmark): World War I: The schooner was shelled and sunk in the North Sea (56.58333°N, -2.75°W) by SMU U-93.
 * SS Gretaston (1901) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean (43.13333°N, -11.53333°W) by SMU UC-27 with the loss of all 29 crew.
 * Heikina (🇳🇱 Netherlands): World War I: The sailing vessel was sunk in the North Sea by SMU UC-44 . Her crew took to the lifeboats but did not survive.
 * SS Mashobra (1914) ( undefined): World War I: The passenger ship was torpedoed and sunk in the Mediterranean Sea 140 nmi south west of Cape Matapan, Greece (35.56667°N, 20.66667°W) by SMU U-28 (Austria-Hungary) with the loss of eight lives. Her captain was taken as a prisoner of war.
 * SS Møhlenpris (1884) (🇳🇴 Norway): World War I: The coaster was sunk in the English Channel 15 nmi south west of Beachy Head, East Sussex, United Kingdom (50.63333°N, -0.25°W) by SMU UB-40 . Her crew survived.
 * SS Panaghi Drakatos (1897) (🇬🇷 Greece): World War I: The cargo ship was sunk in the Atlantic Ocean 26 nmi off Cape Santa Maria, Portugal by SMU U-35 (Germany) . Her crew survived.
 * SS Paris (1910) (🇳🇴 Norway): World War I: The cargo ship was sunk in the North Sea 100 nmi west of Greipengen by SMU U-30 (Germany) . Her crew survived.
 * USS Pike (SS-6) : The Plunger-class submarine sank at Cavite Naval Base, Philippines. She was raised two days later, repaired and returned to service.
 * Sutterton ( undefined): World War I: The trawler was scuttled in the North Sea 65 nmi east south east of St Abb's Head, Berwickshire (55.75°N, -0.25°W) by SMU UC-44 with the loss of a crew member.
 * SS Tusnastabb (1892) (🇳🇴 Norway): World War I: The coaster struck a mine and sank in the English Channel off Cap Gris Nez, Pas-de-Calais, France (50.9°N, 1.56667°W). Her crew survived.

16 April

 *  Amanda (🇸🇪 Sweden): World War I: The brig was scuttled in the North Sea (56.45°N, 3°W) by SMU UC-51 . Her crew survived.
 *  Anne (🇩🇰 Denmark): World War I: The three-masted schooner was scuttled in the Atlantic Ocean west of Ireland (51.75°N, -17.33333°W) by SMU U-43 (Germany) . Her crew survived.
 * HMS C16 : The C-class submarine was rammed and sunk at Harwich, Essex by HMS Melampus (1914) with the loss of all sixteen crew. She was subsequently salvaged, repaired and returned to service.
 * SS Cairndhu (1911) ( undefined): World War I: The cargo ship was torpedoed and sunk in the English Channel 25 nmi west of Beachy Head, East Sussex by SMU UB-40 with the loss of eleven of her crew.
 * SS Crios (1912) (🇬🇷 Greece): World War I: The cargo ship was scuttled in the Atlantic Ocean off Cape Espichel, Portugal (38.33333°N, -9.2°W) by SMU U-52.
 *  Eduard ( undefined): World War I: The three-masted schooner was scuttled in the English Channel 12 nmi south west of Beachy Head (50.56667°N, 0.08333°W) by SMU UC-70 . Her crew survived.
 * Endymion ( undefined): World War I: The sailing vessel was scuttled in the Atlantic Ocean 250 nmi west of Galway, United Kingdom (52.5°N, -16.33333°W) by SMU U-43 (Germany).
 * Lord Chancellor ( undefined): World War I: The trawler was scuttled in the North Sea 50 nmi north east of the Longstone Lighthouse, Northumberland by SMU UC-41 . Her crew survived.
 * SS Marden (1909) ( undefined): World War I: The coaster was shelled and sunk in the English Channel 6 nmi north west of Cap Gris Nez, Pas-de-Calais, France by SMU UB-36  with the loss of a crew member.
 * Polycarp (🇳🇴 Norway): World War I: The sailing vessel was sunk in the North Sea (56.38333°N, 2.86667°W) by SMU UC-51 . Her crew survived.
 * SS Queen Mary (1915) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 180 nmi north west by north of the Fastnet Rock (51.8°N, -14.86667°W) by SMU U-60 with the loss of nine crew.
 *  Rochester Castle ( undefined): World War I: The ketch was shelled and sunk in the English Channel 5 nmi west south west of Cap Gris Nez by SMU UB-36 . Her crew survived.
 * Rosetta (🇪🇬 Egypt): World War I: The sailing vessel was sunk in the Mediterranean Sea off Gaza by SMU UB-42.
 * SS Sagres (1911) (🇵🇹 Portugal): World War I: The cargo shp struck a mine and sank in the Mediterranean Sea off Cap Blanc, Tunisia.
 * ROMANIAN TORPEDO BOAT Smeul : World War I: The torpedo boat struck a mine and sank at Sulina.
 * SS Sontay (1907) (🇫🇷 France): World War I: The passenger ship was sunk in the Mediterranean Sea 100 nmi south east of Malta (35.03333°N, 16.46667°W) by SMU U-33 (Germany) . Her crew survived.
 * SS Towergate (1906) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 250 nmi north west by west of the Fastnet Rock (52.16667°N, -16.26667°W) by SMU U-43 (Germany) . Her crew survived.
 *  Victoria ( undefined): World War I: The three-masted schooner was scuttled in the English Channel 30 nmi south west of Beachy Head by SMU UB-40 . Her crew survived.

17 April

 * SS Aburi (1906) ( undefined): World War I: The Elder Dempster 3,730 grt cargo liner was torpedoed and sunk in the Atlantic Ocean 125 nmi north west of Tory Island, County Donegal (56.25°N, -11.5°W) by SMU U-61 with the loss of 25 crew.
 * SS Bretagne (1912) (🇩🇰 Denmark): World War I: The cargo ship was sunk in the North Sea 8 to 9 nmi off Rattray Head, Aberdeenshire, United Kingdom (57.71667°N, -1.7°W) by SMU UC-45 . Her crew survived.
 * SS Brisbane River (1914) ( undefined): World War I: The cargo ship was scuttled in the Atlantic Ocean 140 nmi west of Gibraltar (35.5°N, -8.16667°W) by SMU U-35 (Germany) . Her crew survived, but her captain was taken as a prisoner of war.
 * SS Cairnhill (1912) ( undefined): World War I: The cargo ship was scuttled in the Atlantic Ocean 160 nmi south west of the Fastnet Rock (52.15°N, -13.26667°W) by SMU U-55 . Her crew survived, but her captain was taken as a prisoner of war.
 * SS Charles Goodanew (1911) ( undefined): World War I: The coaster was sunk in the North Sea 3.5 nmi north north east of Rattray Head (57.65°N, -1.75°W) by SMU UC-45 with the loss of thirteen of her crew.
 * SS Corfu (1907) ( undefined): World War I: The cargo ship was scuttled in the Atlantic Ocean 160 nmi west of Gibraltar (35.23333°N, -8.41667°W) by SMU U-35 (Germany) with the loss of three crew.
 * SS Costante (1898) ( undefined): World War I: The cargo ship was sunk in the Mediterranean Sea off the coast of Algeria (36.88333°N, 4.25°W) by SMU U-32 (Germany).
 *  Dantzic ( undefined): World War I: The schooner was scuttled in the Irish Sea 30 nmi south by west of St. Ann's Head, Pembrokeshire by SMU UC-47 . Her crew survived.
 * SS Donegal (1904) ( undefined): World War I: The hospital ship was torpedoed and sunk in the English Channel 19 nmi south of the Dean Lightship ( undefined) (50.43333°N, -1°W) by SMU UC-21 with the loss of 40 lives.
 * SS Fernmoor (1894) ( undefined): World War I: The cargo ship was scuttled in the Atlantic Ocean 150 nmi west of Gibraltar (35.5°N, -8.3°W) by SMU U-35 (Germany) . Her crew survived.
 * SS Kish (1902) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 160 nmi north west by west of the Fastnet Rock by SMU U-67 with the loss of six crew.
 *  : World War I: The hospital ship was torpedoed and sunk in the English Channel 42 nmi north of Le Havre, Seine-Maritime, France (50.18333°N, 0.2°W) by SMU UB-40 with the loss of 40 lives.
 * SS Robert (1899) (🇩🇰 Denmark): World War I: The cargo ship was torpedoed and sunk in the North Sea 14 nmi east of Fair Isle, United Kingdom by SMU UC-76 with the loss of eight crew.
 * U.S.A. ( undefined): World War I: The fishing vessel was scuttled in the North Sea 16 nmi east north east of the Longstone Lighthouse, Northumberland (55.9°N, -1.1°W) by SMU UC-41 . Her crew survived.
 *  William Shephard ( undefined): World War I: The three-masted schooner was scuttled in the Irish Sea 30 nmi south by west of St. Ann's Head by SMU UC-47 . Her crew survived.

18 April

 * SS Atalanta (1883) (🇸🇪 Sweden): World War I: The cargo ship was sunk in the North Sea (56.55°N, 4.3°W) by SMU U-86 . Her crew survived.
 * SS Bergensgut (1916) (🇳🇴 Norway): World War I: The cargo ship was sunk in the North Sea 60 nmi east of Peterhead, Aberdeenshire, United Kingdom by SMU UC-76 with the loss of ten of her crew.
 * SS Castilian (1890) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 110 nmi north west by north of Tory Island, County Donegal (56.33333°N, -10.75°W) by SMU U-61 with the loss of ten crew.
 * SS Cragoswald (1899) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 60 nmi west by south of the Bishop Rock, Isles of Scilly by SMU U-84 . with the loss of two of her crew.
 * SS Heim (1882) (🇳🇴 Norway): World War I: The cargo ship struck a mine and sank in the English Channel 10 nmi north of Pointe d'Ailly, Seine-Maritime, France with the loss of two of her crew. by SMU UC-71 . Her crew survived.
 * John S. Boyle ( undefined): World War I: The fishing vessel was scuttled in the North Sea 25 nmi east by souht of St Abb's Head, Berwickshire (56.26667°N, -1.55°W) by SMU UC-41 . Her crew survived.
 * SS Louisiana (1896) (🇩🇰 Denmark): World War I: The cargo ship wastorpedoed and sunk in the North Sea 20 nmi) north north east of Buchan Ness, (57.78333°N, -1.36667°W) by SMU UC-45 . Her crew survived.
 * ST Marcel (🇧🇪 Belgium): World War I: The tug was scuttled in the North Sea 8 nmi north east of the Noord Hinder Lightship (🇳🇱 Netherlands) by SMU UB-23.
 * Rameses ( undefined): World War I: The trawler was scuttled in the North Sea 45 nmi east of St Abb's Head (56.23333°N, -1.48333°W) by SMU UC-41 . Her crew survived.
 * SS Rhydwen (1914) ( undefined): World War I: the cargo ship was torpedoed and sunk in the Atlantic Ocean 170 nmi north west by west of the Fastnet Rock (51.66667°N, -14°W) by SMU U-67 with the loss of six crew.
 * SS Rinaldo (1908) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 18 nmi west by north of Cape Cherchell, Algeria (36.58333°N, 1.8°W) by SMU U-32 (Germany) . Her crew survived.
 * SS Rowena (1899) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 95 nmi west by south of the Bishop Rock (49.05°N, -8.41667°W) by SMU U-84 with the loss of a crew member.
 * SS Scalpa (1902) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 150 nmi north west by west of the Fastnet Rock by SMU U-53 . Her crew survived.
 * SS Sculptor (1911) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 120 nmi north west by west of the Fastnet Rock (51.93333°N, -12.83333°W) by SMU U-53 with the loss of a crew member.
 * Surcouf (🇫🇷 France): World War I: The sailing vessel was sunk in the English Channel off Île Vierge, Finistère by SMU UC-26 . Her crew survived.
 *  Thomas ( undefined): World War I: The schooner was scuttled in the Atlantic Ocean 40 nmi off Cape St. Vincent, Portugal by SMU UC-27 . Her crew survived.
 * SS Trekieve (1898) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 100 nmi west of Gibraltar (35°N, -9.75°W) by SMU U-35 (Germany) with the loss of three crew.
 * SS Troldfos (1912) (🇳🇴 Norway): World War I: The cargo ship was sunk in the Atlantic Ocean 50 nmi west north west of the Shetland Islands, United Kingdom by SMU U-93 . Her crew survived.
 *  West Lothian (🇳🇴 Norway): World War I: The four-masted barque was torpedoed and sunk in the Atlantic Ocean 50 nmi west of the Shetland Islands (60.91667°N, -3.5°W) by SMU U-93 . Her crew survived.
 * Witham ( undefined): World War I: The trawler was shelled and sunk in the North Sea 125 nmi east by south of St Abb's Head (55.93333°N, 1.6°W) by SMU UC-50 . Her crew survived.

19 April

 * SS Avocet (1885) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 100 nmi west north west of the Fastnet Rock (51.31667°N, -12.5°W) by SMU U-50 . Her crew survived.
 * Bethlehem ( undefined): World War I: The auxiliary sailing vessel struck a mine and sank in the North Sea with the loss of a crew member.
 * SS Cilurnum (1902) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Bay of Biscay 5 nmi south west of Penmarc'h, Finistère, France (47.75°N, -4.5°W) by SMU UC-21 with the loss of a crew member.
 * SS Ellida (1901) (🇳🇴 Norway): World War I: The cargo ship was sunk in the North Sea 2.5 nmi east north east of Whitby, Yorkshire, United Kingdom by SMU UB-41 . Her crew survived.
 * SS Elswick Manor (1901) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 180 nmi west of Ouessant, Finistère, France (47.6°N, -9.53333°W) by SMU U-84 . Her crew survived.
 * SS Gold Coast (1900) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 14 nmi south of Mine Head, Cornwall (51.76667°N, -7.46667°W) by SMU UC-47 . Her crew survived.
 * SS Howth Head ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 158 nmi north west of the Fastnet Rock (52.33333°N, -13.63333°W) by SMU U-60 with the loss of two crew.
 *  Jewel ( undefined): World War I: The brig was scuttled in St. George's Channel 20 nmi south east of the Coningbeg Lightship ( undefined) by SMU UC-47 . Her crew survived.
 * HMT Lobelia : World War I: The naval trawler struck a mine and sank off Fanad Point, Lough Swilly (55.26667°N, -7.75°W) with the loss of eleven crew.
 * SS Poltava (1899) ( undefined): World War I: The coaster struck a mine and sank in the North Sea 3 nmi east north east of the Souter Point Lighthouse, South Shields, County Durham (54.98333°N, -1.275°W). Her crew survived.
 * SMS Seeadler : The hulk exploded and sank at Wilhelmshaven, Lower Saxony.
 *  Senator Dantziger ( undefined): World War I: the schooner was shelled and sunk in the English Channel 15 nmi south by east of Newhaven, East Sussex by SMU UC-26 . Her crew survived.
 * Senhora da Conceicao (🇵🇹 Portugal): World War I: The sailing vessel was scuttled in the Atlantic Ocean north of Cape Finisterre, Spain (43.63333°N, -10°W) by SMU U-52.
 * SS Sowwell (1900) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 170 nmi west of Gibraltar by SMU U-35 (Germany) with the loss of 21 crew.
 * HMT Star of Freedom : World War I: The naval trawler struck a mine and sank in the Atlantic Ocean off Trevose Head, Cornwall (50.58333°N, -5.41667°W with the loss of ten of her crew.
 * SS Tempus (1904) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 130 nmi north west by west of the Fastnet Rock by SMU U-53 with the loss of a crew member.

20 April

 * SS Annapolis (1911) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 74 nmi north west of Eagle Island, County Mayo (55.75°N, -11.75°W) by SMU U-61 and SMU U-69 (both ). Her crew survived.
 *  August ( undefined): World War I: The barque was sunk in the Atlantic Ocean 300 nmi west of Ireland (50.41667°N, -16.66667°W) by SMU U-43 (Germany).
 * SS Ballochbuie (1905) ( undefined): World War I: The coaster was torpedoed and sunk in the North Sea 7 nmi east of the Isle of May, Fife by SMU UC-41 with the loss of three of her crew.
 * SS Caithness (1898) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 130 nmi north west by north of Cape Ortegal, Spain (45.8°N, -11.11667°W) by SMU U-52 with the loss of 47 crew.
 * Erith ( undefined): World War I: The trawler was scuttled in the North Sea 40 nmi south of Girdleness, Aberdeenshire by SMU UC-44 . Her crew survived.
 * SS Emma (1898) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 200 nmi south west by south of the Fastnet Rock (49.91667°N, -14.66667°W) by SMU U-50 with the loss of two crew.
 * SS Georgios (1913) (🇬🇷 Greece): World War I: The cargo ship was sunk in the Bay of Biscay 11 nmi south east of La Vieille, Finistère, France (47.93333°N, -4.45°W) by SMU UC-21.
 * Grecian ( undefined): World War I: The trawler was scuttled in the North Sea 22 nmi north east by east of the Longstone Lighthouse, Northumberland by SMU UC-44 . Her crew survived.
 * HMT Loch Eye : World War I: The naval trawler struck a mine and sank in the Irish Sea 1.25 nmi south west of Hook Point, County Waterford (52.13333°N, -6.98333°W with the loss of seven of her crew.
 * SS Lowdale (1893) ( undefined): World War I: The collier was shelled and sunk in the Atlantic Ocean 90 nmi west by north of Gibraltar by SMU U-35 (Germany) . Her crew survived.
 * SS Malakand ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 145 nmi west of the Bishop Rock, Isles of Scilly (49.33333°N, -10°W) by SMU U-84 with the loss of a crew member.
 * SS Nentmoor (1903) ( undefined): World War I: The cargo ship was shelled and sunk in the Atlantic Ocean 140 nmi west of Gibraltar (32.41667°N, -8.03333°W) by SMU U-35 (Germany) . Her crew survived.
 * HMS Nepaulin : World War I: The auxiliary minesweeper struck a mine and sank in the North Sea off the Dyck Lightship ( undefined) with the loss of nineteen of her crew.
 * HMT Othonna : World War I: The naval trawler struck a mine and sank in the North Sea (56.28333°N, -2.45°W) with the loss of nine of her crew.
 * SS Portloe (1912) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 160 nmi west north west of the Fastnet Rock (51.21667°N, -14.16667°W) by SMU U-67 with the loss of 24 crew.
 * SS Ringholm (1909) (🇳🇴 Norway): World War I: The coaster was sunk in the North Sea 5 nmi off St. Abb's Head, Berwickshire, United Kingdom by SMU UC-41 . Her crew survived.
 * HMT Ruthin Castle : World War I: The naval trawler struck a mine and sank in the North Sea off Skinningrove, Yorkshire (54.61667°N, -0.88333°W) with the loss of nine of her crew.
 * SS San Hilario (1913) ( undefined): World War I: The tanker was torpedoed and sunk in the Atlantic Ocean 270 nmi west by north of the Fastnet Rock (50.91667°N, -16.46667°W) by SMU U-43 (Germany) . Her crew survived.
 * SS Torr Head (1894) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 160 nmi north west by north of the Fastnet Rock (52.16667°N, -14°W) by SMU U-60 . Her crew survived.

21 April

 * SS Diadem (1916) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 200 nmi south west by west of the Fastnet Rock by SMU U-50 . Her crew survived.
 * Emile et Charlotte (🇫🇷 France): World War I: The fishing vessel was sunk in the Bay of Biscay north east of the Île d'Yeu, Vendée by SMU UC-21 . Her crew survived.
 * SMS G42 : World War I: Battle of Dover Strait: The Großes Torpedoboot 1913-class torpedo boat was rammed and sunk in the Strait of Dover by HMS Broke (1914) with the loss of 36 of her 83 crew.
 * SMS G85 : World War I: Battle of Dover Strait: The Großes Torpedoboot 1913-class torpedo boat was torpedoed and sunk in the Strait of Dover by HMS Swift (1907).
 * SS Gerda (1898) (🇳🇴 Norway): World War I: The coaster was sunk in the North Sea 5 nmi south west of Sumburgh Head, Shetland Islands, United Kingdom by SMU UC-55 . Her crew survived.
 *  Giosue ( undefined): World War I: The brigantine was shelled and sunk in the Mediterranean Sea off Tunis, Tunisia (37.88333°N, 10.1°W) by SMU U-32 (Germany).
 * Jedburgh ( undefined): World War I: The trawler was scuttled in the North Sea (35 nmi north north west of Foula by SMU UC-33 . Her crew survived.
 * SS Peik (1910) (🇳🇴 Norway): World War I: The coaster was sunk in the North Sea 10 nmi north of Coquet Island, Northumberland, United Kingdom by SMU UC-44 . Her crew survived.
 * SS Pontiac (1879) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 56 nmi south west of the Fastnet Rock (50.51667°N, -10.15°W) by SMU U-53 with the loss of two crew.
 * SS Sebek (1909) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 145 nmi north west of Tory Island, County Donegal (56.2°N, -12.33333°W) by SMU U-70 with the loss of a crew member.
 *  Skjold (🇳🇴 Norway): World War I: The barque was shelled and sunk in the Atlantic Ocean west north west of the Fastnet Rock (51.68333°N, -14.61667°W) by SMU U-61 . Her crew survived.
 * SS Telena (1895) ( undefined): World War I: The tanker was torpedoed and sunk in the Atlantic Ocean 170 nmi west north west of the Fastnet Rock (51.26667°N, -14°W) by SMU U-61 . Her crew survived.
 * SMU UC-30 : World War I: The Type UC II submarine struck a mine and sank in the North Sea 66 nmi west of Nymindegab, Denmark with the loss of all 26 crew.
 *  Ville de Dieppe (🇫🇷 France): World War I: The barque was shelled and sunk in the Bay of Biscay west of the Île d'Oléron, Charente-Maritime (45.98333°N, -1.86667°W) by SMU UC-21 . Her crew survived and were rescued by a French Navy submarine.
 * SS Warrior (1901) ( undefined): World War I: The cargo ship struck a mine and sank in the Mediterranean Sea 7 nmi north east of the Fratelli Rocks, Tunisia with the loss of a crew member.
 * Yeovil ( undefined): World War I: The trawler was scuttled in the North Sea 35 nmi north north west of Foula by SMU UC-33 with the loss of a crew member.

22 April

 *  Arethusa ( undefined): World War I: The barque was scuttled in the Atlantic Ocean 15 nmi north west of Eagle Island, County Mayo by SMU UC-66 . Her crew survived.
 * SS Blaatind (🇳🇴 Norway): World War I: The cargo ship was sunk in the Tyrrhenian Sea 30 nmi off Civitavecchia, Lazio, Italy (42.46667°N, 10.98333°W) by SMU U-33 (Germany) with the loss of two crew.
 * SS Capenor (1890) ( undefined): World War I: The cargo ship struck a mine and sank in the Bay of Biscay off La Pallice, Charente-Maritime, France (46.1°N, -1.28333°W). Her crew survived.
 * SS Giskø (🇳🇴 Norway): World War I: The cargo ship was sunk in the North Sea (61.05°N, 3.46667°W by SMU U-21 (Germany) . Her crew survived.
 * SS Godø (1904) (🇳🇴 Norway): World War I: The coaster was sunk in the North Sea 16 nmi east of the Shetland Islands, United Kingdom by SMU UC-41 . Her crew survived.
 * Maria S. ( undefined): World War I: The sailing vessel was sunk in the Tyrrhenian Sea off Civitavecchia by SMU U-33 (Germany).
 * HMML 431 : The motor launch was lost on this date.
 * SS Neepawah (1903) (🇨🇦 Canada): World War I: The cargo ship was scuttled in the Atlantic Ocean 120 nmi south west of the Bishop Rock, Isles of Scilly, United Kingdom by SMU U-53 . Her crew survived.
 * Nightingale ( undefined): World War I: The fishing vessel was scuttled in the North Sea 26 nmi south of Aberdeen by SMU UC-44 . Her crew survived.
 *  Percy Birdsall (🇺🇸 United States): World War I: The schooner was sunk in the Bay of Biscay off the Gironde Estuary by SMU UC-21 . Her crew survived.
 * SS Theodore William (🇳🇴 Norway): World War I: The cargo ship was sunk in the North Sea 40 nmi off the Shetland Islands (60.75°N, 0.21667°W) by SMU U-21 (Germany) . Her crew survived.
 *  Unione ( undefined): World War I: The brigantine was sunk in the Tyrrhenian Sea off Civitavecchia (42.01667°N, 10.9°W) by SMU U-33 (Germany).
 *  Valerie (🇳🇴 Norway): World War I: The barque was shelled and sunk in the Bay of Biscay 30 nmi west of the Cordouan Lighthouse, Charente Maritime by SMU UC-21 . Her crew survived.
 *  Vestelv (🇳🇴 Norway): World War I: The full-rigged ship was scuttled in the Atlantic Ocean 14 nmi off Tory Island, County Donegal, United Kingdom by SMU U-93 . Her crew survived.
 *  Woodward Abrahams (🇺🇸 United States): World War I: The three-masted schooner was sunk in the Atlantic Ocean 407 nmi west of the Fastnet Rock by SMU U-43 (Germany) . Her crew survived.

23 April

 *  Acadian (🇳🇴 Norway): World War I: The barque was scuttled in the Atlantic Ocean 65 nmi north west of Tory Island, County Donegal, United Kingdom (55.73333°N, -9.5°W) by SMU U-52 . Her crew survived.
 * SS Auriac (1890) ( undefined): World War I: The coaster was shelled and sunk in the North Sea 5 nmi east south east of St Abb's Head, Berwickshire by SMU UC-44 with the loss of a crew member.
 * SS Bandiera E. Moro (1891) ( undefined): World War I: The cargo ship was sunk in the Atlantic Ocean 50 nmi west of Tangier, Morocco by SMU U-35 (Germany) . Her crew survived.
 * SS Baron Stjernblad (1890) (🇩🇰 Denmark): World War I: The coaster was sunk in the North Sea 5 nmi north east of Eyemouth, Berwickshire by SMU UC-44 . Her crew survived.
 * Boro ( undefined): World War I: The sailing vessel was sunk in the Aegean Sea east of Rhodes, Greece by SMU UB-42.
 *  Calluna (🇩🇰 Denmark): World War I: The barque was sunk in the Atlantic Ocean south west of the Isles of Scilly, United Kingdom (48.85°N, -8.63333°W) by SMU U-61 . Her crew survived.
 * Cenobic (🇧🇪 Belgium): World War I: The fishing vessel struck a mine and sank in the English Channel off Le Tréport, Seine-Maritime, France with the loss of four of her crew.
 * SS Dykland (1914) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 200 nmi west north west of the Fastnet Rock by SMU U-50 . Her crew survived.
 * SS Eptapyrgion (1914) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 150 nmi west of the Isles of Scilly by SMU U-53 . Her crew survived.
 * SS Imataka (1911) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Irish Sea 15 nmi south south west of the Daunt Rock by SMU UC-47 . Her crew survived.
 * SS Lena (1904) ( undefined): World War I: The cargo ship was sunk in the Atlantic Ocean south west of the Isles of Scilly (48.75°N, -8.5°W) by SMU U-61 with the loss of all 25 crew.
 * HMT Lena Melling : World War I: The naval trawler struck a mine and sank in the North Sea off the Elbow Lightship ( undefined) (51.375°N, 1.55833°W) with the loss of eleven of her crew.
 *  Marita (🇳🇴 Norway): World War I: The full-rigged ship was sunk in the Atlantic Ocean 110 nmi west of St. Kilda, Inverness-shire, United Kingdom (58.35°N, -10.56667°W) by SMU U-82 . Her crew survived.
 * SS Oswald (1915) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 200 nmi south west of the Fastnet Rock by SMU U-50 . Her crew survived.
 * HMT Rose II : World War I: The naval trawler struck a mine and sank in the Irish Sea off Belfast, County Down (54.73333°N, -5.63333°W) with the loss of six of her crew.
 * SS Savio (1888) ( undefined): World War I: The cargo ship was sunk in the Bay of Biscay 20 nmi south east of Belle Île, Morbihan, France by SMU UC-36 . Her crew survived.
 * SS Scot (1895) (🇩🇰 Denmark): World War I: The cargo ship was sunk in the North Sea 12 nmi east by north of St Abb's Head (56.03333°N, -1.76667°W) by SMU UC-44 . Her crew survived.
 * SS Stegg (1883) (🇳🇴 Norway): World War I: The coaster was sunk in the North Sea (60 nmi east of Lerwick, Shetland Islands, United Kingdom (60.68333°N, 0.61667°W) by SMU UC-41 with the loss of a crew member.
 *  Svanen (🇩🇰 Denmark): World War I: The full-rigged ship was sunk in the Atlantic Ocean 30 nmi west north west of Muckle Flugga, Shetland Islands by SMU U-60 with the loss of two crew.

24 April

 * SS Abosso (1912) ( undefined): World War I: SS Abosso was a British merchant ship of 7,782 tons owned by the Elder Dempster. Built 1912 by Harland & Wolff and powered by a steam triple expansion engine of 516nhp giving 13 knots. On 24 April 1917 Abosso carrying passengers, mail and gold, was torpedoed and sunk 180 miles W by N of Fastnet, Ireland by German submarine SMU U-43 (Germany) . Loss of 65 lives.
 *  Amulree ( undefined): World War I: The barque was sunk in the Atlantic Ocean 50 nmi north by east of Tory Island, County Donegal (56.16667°N, -8.66667°W) by SMU U-81 . Her crew survived.
 * SS Anglesea (1914) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 160 nmi south west of the Bishop Rock, Isles of Scilly (48.93333°N, -10.28333°W) by SMU U-53 . Her crew survived.
 * SS Barnton (1904) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Bay of Biscay 40 nmi west by south of Pointe de Chassiron, Île d'Oléron, Charente-Maritime, France (45.66667°N, -2.2°W) by SMU UC-21 with the loss of fourteen of her crew.
 * Bien Aime Prof. Luigi ( undefined): World War I: The sailing vessel was scuttled in the Atlantic Ocean off Cape St. Vincent, Portugal (36.88333°N, -9.16667°W) by SMU U-35 (Germany).
 *  Clan Galbraith (🇳🇴 Norway): World War I: The four-masted barque was scuttled in the Atlantic Ocean west of Ireland (52.5°N, -14°W) by SMU U-70 . Her crew survived.
 *  Cordelia (🇸🇪 Sweden): World War I: The barque was shelled and sunk in the Atlantic Ocean (51.13333°N, -15.21667°W) by SMU U-43 (Germany) . Her crew survived.
 *  Eos (🇩🇰 Denmark): World War I: The three-masted schooner was sunk in the Atlantic Ocean west of Ireland (52.66667°N, -14.75°W) by SMU U-70 . Her crew survived.
 * SS Ferndene (1899) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 150 nmi west of the Bishop Rock by SMU U-53 with the loss of nine crew.
 * Heather ( undefined): World War I: The drifter was scuttled in the Atlantic Ocean 14 nmi west by nort of the Bishop Rock (49.86667°N, -6.8°W) by SMU UC-47 . Her crew survived.
 * SS Kenilworth (1895) ( undefined): World War I: The cargo ship struck a mine and sank in the Atlantic Ocean 3.5 nmi west by south of Point St. Mathieu, Finistère, France (48.28333°N, -4.8°W) by SMU UC-36 . Her crew survived.
 *  La Providence (🇫🇷 France): World War I: The schooner was sunk in the Loire Estuary by SMU UC-36.
 * HMT Margate : World War I: The naval trawler was shelled and sunk in the North Sea off Spurn Head, Yorkshire by SMU UC-50 with the loss of thirteen of her crew.
 * Marie Blanche (🇫🇷 France): World War I: The sailing vessel was sunk in the English Channel 30 nmi north of Cherbourg, Seine Maritime (50.13333°N, -1.61667°W) by SMU UB-32 with the loss of a crew member.
 * Mayfly ( undefined): World War I: The trawler was shelled and sunk in the North Sea 75 nmi north east by east of Scarborough, Yorkshire by SMU UC-50 with the loss of three of her crew.
 *  Metropolis (🇳🇴 Norway): World War I: The four-masted barque was scuttled in the Atlantic Ocean south west of the Isles of Scilly (48.5°N, -11.25°W) by SMU U-61 . Her crew survived.
 * SS Minister Tak van Poortvliet (1899) (🇳🇱 Netherlands): World War I: The cargo ship was torpedoed and sunk in the North Sea 20 nmi off IJmuiden, North Holland (52.7°N, 3.53333°W) by SMU UB-10.
 * SS Nordsøen (1901) (🇩🇰 Denmark): World War I: The cargo ship was scuttled in the Atlantic Ocean off Cape St. Vincent (37.03333°N, -8.9°W) by SMU U-35 (Germany) . Her crew survived.
 * SS Plutus (1910) ( undefined): World War I: The collier was torpedoed and sunk in the Atlantic Ocean 9 nmi north West of Trevose Head, Cornwall (50.68333°N, -5.11667°W) by SMU UC-47 with the loss if a crew member.
 * SS Thistleard (1912) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 135 nmi west north west of Tory Island (55.16667°N, -12°W) by SMU U-82 . Her crew survived.
 * SS Torvore (1882) (🇳🇴 Norway): World War I: The cargo ship was sunk in the Atlantic Ocean off Cape St. Vincent (37°N, -8.9°W) by SMU U-35 (Germany) . Her crew survived.
 * Upton Castle ( undefined): World War I: The trawler was scuttled in the North Sea 60 nmi east of the Longstone Lighthouse, Northumberland by SMU UC-29 . Her crew survived.
 *  Valkyrian (🇸🇪 Sweden): World War I: The three-masted schooner was shelled and sunk in the Atlantic Ocean south west of Ireland by SMU U-70 with the loss of a crew member.
 *  Vestdal (🇳🇴 Norway): World War I: The full-rigged ship was shelled and sunk in the Atlantic Ocean 280 nmi west of Ireland (52.31667°N, -15.3°W) by SMU U-70 with the loss of a crew member.
 * SS Vilhelm Krag (1899) (🇳🇴 Norway): World War I: The cargo ship was sunk in the Atlantic Ocean 5 nmi west of the Pildale Lighthouse, Portugal (37.05°N, -8.73333°W) by SMU U-35 (Germany) . Her crew survived.

25 April

 * SS Abosso (1912) ( undefined): World War I: The passenger ship was torpedoed and sunk in the Atlantic Ocean 180 nmi west by north of the Fastnet Rock (57.16667°N, -14.96667°W) by SMU U-43 (Germany) with the loss of 65 lives.
 * SS Baigorry (1889) (🇫🇷 France): World War I: The cargo ship was scuttled in the Bay of Biscay 15 nmi south south east of Belle Île, Morbihan (47.06667°N, -2.9°W) by SMU UC-21 . Her crew survived.
 * SS Ballarat (1911) ( undefined): World War I: The troopship was torpedoed and damaged in the Atlantic Ocean 24 nmi south by west of the Wolf Rock, Cornwall (49.55°N, -5.6°W) by SMU UB-32 . She was taken under tow but consequently sank (49.8625°N, -5.31667°W). Her crew survived.
 *  Elisabeth (🇩🇰 Denmark): World War I: An attempt was made to scuttle the schooner in the Atlantic Ocean 70 to 80 nmi south west of Ireland (51.03333°N, -12.08333°W) by SMU U-53 . The derelict ship was discovered 180 nmi) north west of the Fastnet Rock on 30 April by SMU U-81, which also attempted to scuttle her, but she was kept afloat by her cargo of Pitch Pine. Although declared a constructive total loss, she was subsequently repaired and returned to service.
 * Elizabeth (🇳🇱 Netherlands): World War I: The lugger was scuttled in the North Sea (52.6°N, 3.66667°W) by SMU UB-10 . Her crew survived.
 *  Este (🇩🇰 Denmark): World War I: The barque was sunk in the North Sea 50 nmi west of Egerø, Norway (58.41667°N, 3.8°W) by SMU UB-34 . Her crew survived.
 * FRENCH DESTROYER Etendard : World War I: The Branlebas-class destroyer was torpedoed and sunk in the North Sea off Dunquerque, Nord with the loss of all hands.
 *  Glenesk (🇳🇴 Norway): World War I: The barque was scuttled in the Atlantic Ocean 75 nmi west north west of Eagle Island, County Mayo, United Kingdom by SMU U-81 . Her crew survived.
 *  Havila (🇩🇰 Denmark): World War I: The barque was sunk on the Atlantic Ocean 15 nmi east north east of North Rona,United Kingdom by SMU U-58 . Her crew survived.
 *  Hawthornbank (🇩🇰 Denmark): World War I: The barque was sunk in the Atlantic Ocean 35 nmi north by east of North Rona by SMU U-58 with the loss of nine crew.
 *  Heathfield (🇳🇴 Norway): World War I: The barque was scuttled in the Atlantic Ocean 53 nmi west by north of Eagle Island by SMU U-81 . Her crew survived.
 * SS Hesperides (1899) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 130 nmi north west of the Fastnet Rock (52°N, -13.83333°W) by SMU U-69 with the loss of a crew member.
 * SS Hirondelle (1890) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Bay of Biscay 13 nmi south by east of Belle Île, Morbihan, France by SMU UC-36 . Her crew survived.
 *  Invermay ( undefined): World War I: The barque was scuttled in the Atlantic Ocean 40 nmi north west by north of Eagle Island (54.66667°N, -11°W) by SMU U-81 . Her crew survived.
 *  Laura ( undefined): World War I: The schooner was set afire and sunk in the Atlantic Ocean 150 nmi west north west of the Fastnet Rock (51.33333°N, -13.5°W) by SMU U-53 . Her crew survived.
 * SS Stephanosis (1904) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 180 nmi south west of the Fastnet Rock by SMU U-82 with the loss of six of her crew.
 *  Sokoto (🇩🇰 Denmark): World War I: The barque was sunk in the Atlantic Ocean 15 nmi north east by north of North Rona by SMU U-58 . Her crew survived.
 * SS Swanmore (1913) ( undefined): World War I: The cargo ship was shelled and damaged in the Atlantic Ocean 230 nmi west north west of the Fastnet Rock by SMU U-43 (Germany) and SMU U-93 (both ) She was then torpedoed and sunk by SMU U-50 with the loss of eleven crew.

26 April

 * Active ( undefined): World War I: The trawler was scuttled in the North Sea 65 nmi east by south of the Longstone Lighthouse by SMU UC-50 . Her crew survived.
 * Agnes Cairns ( undefined): World War I: The sailing vessel was scuttled in the English Channel 8 nmi north east of Alderney, Channel Islands by SMU UC-65 . Her crew survived.
 *  Aigle (🇫🇷 France): World War I: The brigantine was scuttled in the English Channel 11 nmi south west of Start Point, Devon, United Kingdom by SMU UC-47.
 * SS Alhama (1899) ( undefined): World War I: The cargo ship struck a mine and sank in the English Channel off Calais, Pas-de-Calais, France. Her crew survived.
 * Amsteldijk (🇳🇱 Netherlands): World War I: The trawler was sunk in the North Sea off the Haaks Lightship (🇳🇱 Netherlands) (52.93333°N, 4.16667°W) by SMU UC-63 . Her crew were rescued by the trawler Voorbode (🇳🇱 Netherlands.
 *  Athole ( undefined): World War I: The auxiliary ketch was shelled and sunk in the English Channel 20 nmi south of the Owers Lightship ( undefined) by SMU UC-65 . Her crew survived.
 *  Augusta ( undefined): The barque was scuttled in the Mediterranean Sea north east of Cap Bon, Tunisia (37.36667°N, 11.51667°W) by SMU UC-27.
 * Boy Dennis ( undefined): World War I: The fishing vessel was scuttled in the English Channel 10 nmi south south west of Start Point, Devon by SMU UC-21 . Her crew survived.
 * Bretagne et Vendée (🇫🇷 France): World War I: The sailing vessel was sunk in the English Channel off Alderney (49.85°N, -2.06667°W) by SMU UC-65.
 * SS Chertsey (1898) ( undefined): World War I: The collier was torpedoed and sunk in the Mediterranean Sea 4 nmi north of Algiers, Algeria (36.86667°N, -3.08333°W) by SMU UC-67 . Her crew survived.
 * Ehrglis ( undefined): World War I: The sailing vessel was set afire and sunk in the Atlantic Ocean (51.83333°N, -17.81667°W) by SMU U-43 (Germany).
 *  Gennarino ( undefined): World War I: The three-masted schooner was scuttled in the Mediterranean Sea off Cap Bon (37.43333°N, 11.43333°W) by SMU UC-27.
 * SS Harflete (1913) ( undefined): World War I: The cargo ship was torpedoed, shelled and sunk in the Atlantic Ocean 200 nmi north west by west of the Fastnet Rock (51.9°N, -14.8°W) by SMU U-70 with the loss of a crew member.
 *  Hekla (🇳🇴 Norway): World War I: The three-masted schooner was sunk in the Atlantic Ocean 120 nmi north west of the Slyne Head Lighthouse, County Galway, United Kingdom by SMU U-53 . Her crew survived.
 * SS Hektoria (1892) (🇳🇴 Norway): World War I: The cargo ship was sunk in the Atlantic Ocean (50.63333°N, -18.66667°W) by SMU U-43 (Germany) . Her crew survived.
 *  John Lockett (🇳🇴 Norway): World War I: The barque was scuttled in the English Channel 25 nmi south of The Lizard, Cornwall, United Kingdom (49.53333°N, -5.08333°W) by SMU UC-47 . Her crew survived.
 * Kong Oscar II (🇳🇴 Norway): World War I: The sailing vessel was sunk in the Seine Estuary by SMU UB-38 . Her crew survived.
 *  Monitor ( undefined): World War I: The schooner was scuttled in the Mediterranean Sea 20 nmi south by east of Cap d'Antibes, Alpes-Maritimes, France (43.18333°N, 7.86667°W) by SMU U-33 (Germany) . Her crew survived.
 * HMT Plantin : World War I: The naval trawler struck a mine and sank in the English Channel 3 nmi east of Anvil Point, Dorset with the loss of nine of her crew.
 * HMT Repro : World War I: The naval trawler struck a mine and sank in the North Sea off Tod Head, Aberdeenshire (56.88333°N, -2.13333°W) with the loss of thirteen of her crew.
 * SS Rio Lages (1900) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 155 nmi north west by north of the Fastnet Rock (51.63333°N, -12.86667°W) by SMU U-69 with the loss of three of her crew.
 * Telefon (🇳🇴 Norway): World War I: The sailing vessel was sunk in the North Sea (54.95°N, 1.8°W) by SMU UC-50 . Her crew survived.
 * SS Vauxhall (1900) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 110 nmi north west by west of the Fastnet Rock (51.75°N, -12.5°W) by SMU U-69 with the loss of two of her crew.

27 April

 * HMT Agile : World War I: The naval trawler struck a mine and sank in the North Sea 3 nmi east of the Sunk Lightship ( undefined) with the loss of three of her crew.
 * HMS Alfalfa : World War I: The collier was sunk in the Atlantic Ocean 30 nmi off the Isles of Scilly (49.25°N, -6.33333°W) by SMU UB-32 with the loss of 30 crew.
 * SS Beemah (1914) ( undefined): World War I: The collier was torpedoed and sunk in the Atlantic Ocean 30 nmi south west by south of the Bishop Rock, Isles of Scilly by SMU UB-32 with the loss of three of her crew.
 *  Burrowa ( undefined): The four-masted barque was scuttled in the Atlantic Ocean 60 nmi west of the Isles of Scilly by SMU UC-65 . Her crew survived.
 * SS Dromore (1913) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 140 nmi west of Tory Island, County Donegal (56.5°N, -11.66667°W) by SMU U-58 . Her crew survived.
 * SS Dunmore Head (1889) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 135 nmi west of Tory Island (56.2°N, -12°W) by SMU U-62 . Her crew survived.
 * SS Glencluny (1909) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 4 nmi north west of Cape Sigli, Algeria by SMU UC-67 with the loss of four of her crew.
 *  Good Hope ( undefined): World War I: The ketch was shelled and sunk in the English Channel 15 nmi north north west of Barfleur, Manche, France by SMU UC-72 . Her crew survived.
 *  Inveramsay ( undefined): World War I: The barque was shelled and sunk in the Atlantic Ocean north west of Ireland (56°N, -11.5°W) by SMU U-62 with the loss of all hands.
 *  Jessie ( undefined): World War I: The schooner was scuttled in the English Channel 7 nmi west of Portland Bill, Dorset by SMU UB-38 . Her crew survived.
 * SS Karuma (1910) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Mediterranean Sea 5 nmi north of Cape Sigle (37.15°N, 4.83333°W) by SMU UC-67 with the loss of two of her crew.
 * SS Langfond (1914) (🇳🇴 Norway): World War I: The cargo ship was sunk in the Atlantic Ocean (58.81667°N, -10.88333°W) by SMU U-58 . Her crew survived.
 *  Mafalda ( undefined): World War I: The brigantine was scuttled in the Mediterranean Sea (43.1°N, 7.66667°W) by SMU U-33 (Germany).
 * SS Manchester Citizen (1912) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 240 nmi north west of the Fastnet Rock (52.5°N, -15.66667°W) by SMU U-70 with the loss of a crew member.
 *  Margaret B. Rouss (🇺🇸 United States): The schooner was sunk in the Mediterranean Sea 42 nmi south of Monaco by SMU U-33 (Germany) . Her crew survived.
 * SS Nidelven (1908) (🇳🇴 Norway): World War I: The cargo ship struck a mine and sank in the North Sea 10 nmi north east of Coquet Island, Northumberland, United Kingdom (55.48333°N, -1.45°W) with the loss of three of her crew.
 * SS Ragnhild (1909) (🇳🇴 Norway): World War I: The cargo ship struck a mine and sank in the North Sea 10 nmi north of the mouth of the River Tyne (55.26667°N, -1.36667°W) with the loss of two of her crew.
 * SS Uranus (1900) ( undefined): World War I: The cargo ship was sunk in the Atlantic Ocean 60 nmi west of the Fastnet Rock by SMU U-81.
 * SS Verjø (1903) (🇳🇴 Norway): World War I: The cargo ship was sunk in the Atlantic Ocean 10 nmi north of the Stiff Lighthouse, Ouessant, Finistère, France by SMU UC-36 with the loss of ten of her crew.

28 April

 * SS Alu Mendi (1907) (🇪🇸 Spain): World War I: The cargo ship was sunk in the Atlantic Ocean 12 nmi south south east of the Tuskar Rock, Ireland by SMU UC-65.
 * Anne Marie (🇳🇴 Norway): World War I: The sailing vessel was sunk in the Atlantic Ocean 160 nmi north west of Ireland by SMU U-70 . Her crew survived.
 * SS Bullmouth (1893) ( undefined): World War I: The tanker was torpedoed and sunk in the Atlantic Ocean 125 nmi north west by west of Tory Island, County Donegal (58.56667°N, -10.83333°W) by SMU U-58 . Her crew survived.
 * Carmelo Padre ( undefined): World War I: The sailing vessel was sunk in the Strait of Messina by SMU U-63 (Germany).
 * SS Condor (1904) ( undefined): World War I: The cargo ship was sunk in the Atlantic Ocean 90 nmi west of Ouessant, Finistère, France by SMU UC-36.
 *  Diana (🇩🇰 Denmark): World War I: The barquentine was damaged in the Atlantic Ocean 200 nmi south west of the Fastnet Rock (49.66667°N, -13.16667°W) by SMU U-93 . She was subsequently towed in to Queenstown, County Cork, United Kingdom where she was declared a total loss. Diana was later repaired and returned to service.
 * Giuseppe Padre I ( undefined): World War I: The sailing vessel was sunk in the Strait of Messina by SMU U-63 (Germany).
 * Giuseppina G. ( undefined): World War I: The sailing vessel was sunk in the Strait of Messina by SMU U-63 (Germany).
 * I Due Fratelli P. ( undefined): World War I: The sailing vessel was sunk in the Strait of Messina by SMU U-63 (Germany).
 * SS Jose de Larrinaga (1913) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 150 nmi west north west of the Fastnet Rock (51.53333°N, -13.33333°W) by SMU U-81 with the loss of twelve crew.
 * Juliette (🇫🇷 France): World War I: The sailing vessel struck a mine and sank in the Mediterranean Sea off Mostaganem, Algeria.
 * SS Karonga (1907) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Strait of Messina 2 nmi south south east of Cape Schio, Italy by SMU U-63 (Germany) with the loss of eighteen crew. Her captain was taken as a prisoner of war.
 * Lisetta ( undefined): World War I: The fishing vessel was sunk in the Mediterranean Sea 8 nmi west of the Îles Sanguinaires, France by SMU U-33 (Germany) . Her crew survived.
 * RMS Medina (1911) ( undefined): World War I: The passenger ship was torpedoed and sunk in the English Channel off Start Point, Devon (50.25°N, -3.5°W) by SMU UB-31.
 * Natale B. ( undefined): World War I: The sailing vessel was sunk in the Strait of Messina by SMU U-63 (Germany).
 * Niobe ( undefined): World War I: The sailing vessel was sunk in the Mediterranean Sea off Malta by SMU UC-37.
 * SS Olga (1880) ( undefined): World War I: The cargo ship was shelled and sunk in the Barents Sea 89 nmi off the North Cape, Finnmark, Norway by SMU U-45.
 * SS Pontiac (1903) ( undefined): World War I: The cargo ship was sunk in the Mediterranean Sea 70 nmi north east of Marsa Susa, Libya (34.06667°N, 22.1°W) by SMU UC-74 with the loss of a crew member. Four of the survivors were taken as prisoners of war.
 *  Port Jackson ( undefined): World War I: The four-masted barque was torpedoed and sunk in the Atlantic Ocean 180 nmi west by north of the Fastnet Rock (51°N, -14.03333°W) by SMU U-67 with the loss of fourteen crew.
 * Pursue ( undefined): World War I: The fishing vessel was scuttled in the English Channel 12 nmi south west of Bolt Head, Devon by SMU UB-32 . Her crew survived.
 * San Francesco Di Paola ( undefined): World War I: The sailing vessel was sunk in the Strait of Messina by SMU U-63 (Germany).
 * SS Teakwood (1902) ( undefined): World War I: The tanker was torpedoed and sunk in the Aegean Sea 26 nmi south west by west of Sapientza, Greece (36.65°N, 21.16667°W) by SMU U-14 (Austria-Hungary) . Her crew survived.
 * SS Terence (1902) ( undefined): World War I: The cargo ship was shelled and sunk in the Atlantic Ocean 150 nmi west by north of the Fastnet Rock (52.66667°N, -12.91667°W) by SMU U-81 with the loss of a crew member.
 * SS Vacuum (1912) (🇺🇸 United States): World War I: The tanker was sunk in the Atlantic Ocean 120 nmi west of Barra, Outer Hebrides, United Kingdom (57.33333°N, -10.16667°W) by SMU U-44 with the loss of 24 crew.

29 April

 *  Askepot (🇳🇴 Norway): World War I: The full-rigged ship was scuttled in the Atlantic Ocean 125 nmi west of the Isles of Scilly, United Kingdom (49.8°N, -9.28333°W) by SMU U-21 (Germany) . Her crew survived.
 * Bayonnais (🇫🇷 France): World War I: The fishing vessel was scuttled in the Bay of Biscay off Guilvinec, Finistère by SMU UC-72 with the loss of all four crew.
 * SS Carbo I (1905) (🇩🇰 Denmark): World War I: The cargo ship was sunk in the North Sea (55.93333°N, 2.1°W) by SMU UC-29 . Her crew survived.
 * SS Comedian (1901) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 200 nmi west of the Bishop Rock, Isles of Scilly (48.1°N, -10.75°W) by SMU U-93 . Her crew survived.
 * SS Daleby (1900) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 180 nmi north west of the Fastnet Rock by SMU U-70 with the loss of 25 crew.
 * Dilston Castle ( undefined): World War I: The trawler was scuttled in the North Sea 16 nmi east by south of Aberdeen (57.16667°N, -1.53333°W) by SMU UB-22 . Her crew survived.
 *  Ellen Harrison ( undefined): World War I: The schooner was shelled and sunk in the English Channel 7 nmi north west of Cherbourg, Seine-Maritime, France by SMU UB-32 . Her crew survived.
 * Eugènie et Lucie (🇫🇷 France): World War I: The sailing vessel was sunk in the Bay of Biscay off Audierne, Finistère by SMU UC-72.
 * Frère des Cinq Soeurs (🇫🇷 France): World War I: The sailing vessel was sunk in the Bay of Biscay off Audierne by SMU UC-72 Her crew survived.
 * Giuseppe Maria ( undefined): World War I: The sailing vessel was sunk in the Strait of Sicily by SMU UC-37.
 * SS Hurlford (1905) ( undefined): The collier was wrecked in Gunna Sound, Scotland.
 * SS Ikbal (1894) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 200 nmi west by south of the Bishop Rock (48.56667°N, -12.58333°W) by SMU U-93 . Her crew survived, but three of them were taken as prisoners of war.
 * Mermaid ( undefined): World War I: The schooner was scuttled in the English Channel 18 nmi south south west of Anvil Point, Devon by SMU UB-32 . Her crew survived.
 * Petit Ernest (🇫🇷 France): World War I: The fishing vessel was scuttled in the Bay of Biscay off Guilvinec by SMU UC-72 with the loss of all three crew.
 * SS Victoria (1887) ( undefined): World War I: The cargo ship was torpedoed and sunk in the North Sea 5 nmi north east by north of Scarborough, Yorkshire by SMU UB-21 with the loss of a crew member.

30 April

 * HMT Arfon : World War I: The naval trawler struck a mine and sank in the English Channel off St Alban's Head, Dorset (50.5°N, -2.16667°W) with the loss of ten of her crew.
 * Argo ( undefined): World War I: The trawler was shelled and sunk in the North Sea 15 nmi east of Buchan Ness, Aberdeenshire by SMU UB-22 . Her crew survived.
 * SS Ascaro (1891) ( undefined): World War I: The cargo ship was sunk in the Atlantic Ocean south west of Ireland (49.16667°N, -11.66667°W) by SMU U-93.
 *  Borrowdale ( undefined): World War I: The barque was stopped and sunk in the Atlantic Ocean south of Ireland (49°N, -10.33333°W) by SMU U-21 (Germany) . Her crew survived.
 * SS Chrisomalli Th. Sifneo (1892) (🇬🇷 Greece): World War I: The cargo ship was sunk in the Mediterranean Sea east of Algiers, Algeria (36.91667°N, 4.03333°W) by SMU U-33 (Germany) . Her crew survived.
 * SS Colbert (1908) (🇫🇷 France): World War I: The troopship was torpedoed and sunk in the Mediterranean Sea (37.08333°N, 8.36667°W) by SMU UC-37 with the loss of 51 lives.
 * SS Delamere (1915) ( undefined): World War I: The UAC 1,525 tons cargo ship was torpedoed and sunk in the Atlantic Ocean 110 nmi west by north of the Fastnet Rock (51.66667°N, -13°W) by SMU U-70 with the loss of ten crew.
 * SS Eden (1879) (🇳🇴 Norway): World War I: The cargo ship was sunk in the English Channel off Worthing, West Sussex, United Kingdom (50.8°N, -0.36667°W) by SMU UC-70 . Her crew survived.
 * SS Fortunata (1883) ( undefined): World War I: The cargo ship was sunk in the Atlantic Ocean 130 nmi west of the Fastnet Rock by SMU U-62 . Her crew survived.
 * SS Gorizia (1907) (🇺🇾 Uruguay): World War I: The cargo ship struck a mine and sank in the English Channel 17 nmi west by north of Portland Bill, Dorset (50.6°N, -2.91667°W).
 * SS Horsa (1894) ( undefined): World War I: The cargo ship was torpedoed and sunk in the Atlantic Ocean 195 nmi south west by west of the Fastnet Rock (48.71667°N, -12.58333°W) by SMU U-93 with the loss of eleven of her crew. One of the survivors was taken as a prisoner of war.
 * Jarstein (🇳🇴 Norway): World War I: The sailing vessel was sunk in the North Sea 80 nmi south west by west of the Egerä Lighthouse (57.58333°N, 4.25°W) by SMU U-61 . Her crew survived.
 *  Little Mystery ( undefined): World War I: The schooner was scuttled in the English Channel off Portland Bill by SMU UC-61 . Her crew survived.
 * SS Parthenon (1904) (🇬🇷 Greece): World War I: The cargo ship was sunk in the Atlantic Ocean 200 nmi south west of the Fastnet Rock (49.41667°N, -11.96667°W) by SMU U-93.
 * SS Portbail (1904) (🇫🇷 France): World War I: The coaster was sunk in the English Channel north east of Cap Barfleur, Manche (50.08333°N, -0.91667°W) by SMU UB-32 . Her crew survived.
 * HMS Tulip (1916) : World War I: The Aubretia-class sloop, operating as a Q-ship, was torpedoed and sunk in the Atlantic Ocean south west of Ireland by SMU U-62 with the loss of 102 crew. Her captain survived and was taken as a prisoner of war.

Unknown date

 * Agia (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea off the coast of North Africa by SMU UC-22.
 * Evangelistria (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea off the coast of North Africa by SMU UC-22.
 * Kyriotis (🇬🇷 Greece): World War I: The sailing vessel was sunk in the Mediterranean Sea off the coast of North Africa by SMU UC-22 . Her crew survived.