SM UC-55

SM UC-55 was a German Type UC II minelaying submarine or U-boat in the German Imperial Navy (Kaiserliche Marine) during World War I. The U-boat was ordered on 12 January 1916, laid down on 25 February 1916, and was launched on 2 August 1916. She was commissioned into the German Imperial Navy on 15 November 1916 as SM UC-55.

Service
In 6 patrols UC-55 was credited with sinking 9 ships, either by torpedo or by mines laid.

Loss
UC-55 sailed from Heligoland on 25 September 1917 to lay mines in the Lerwick Channel, the southern approach to the port of Lerwick in the Shetland Islands. On 29 September, just as she started dropping her mines, she suffered a loss of trim which resulted in her diving beyond her rated maximum dive depth. This in turn resulted in the forward compartment flooding, the batteries failing, and chlorine gas developing. She was forced to surface to ventilate the boat, but when she surfaced, the rudder refused to answer the helm due to the lack of battery power. Her captain then gave orders to destroy secret documents and codebooks and set scuttling charges in the mine room and engine room. While the charges were being placed she was sighted by the armed trawler Moravia and the destroyers HMS Tirade (1917) and HMS Sylvia (1897).

A 12-pdr shell from the Sylvia hit the submarine's conning tower, killing her commander, Horst Ruhle von Lilienstern, and a second shell hit the hull and she began to sink, after which two depth-charges were dropped right beside the UC-55, resulting in the U-boat blowing up. The Moravia then closed with the wreck, fired two more shots into her, and dropped a final depth-charge. Of the submarine's crew, 17 were taken prisoner, and 10 were killed.

Location of Wreck
The wreck of UC-55 is thought to lie in 100 m at 60.05361°N, -0.96583°W. This site was surveyed on 3 July 1985, when side scan sonar discovered the wreck of a submarine lying on its keel, and measuring approximately 5.6 m high and 50 m long.