German submarine U-978

German submarine U-978 was a World War II German Type VIIC U-boat operated by the Kriegsmarine. She holds the distiniction of having completed the longest underwater patrol of World War II.

Service history
U-978 was commissioned on 12 May 1943 and assigned to 5th U-boat Flotilla for crew training. On 1 August 1944, U-978 was assigned to 3rd U-boat Flotilla for operational service, and completed one patrol with that unit. On 4 September 1944 she was ordered to 11th U-boat Flotilla, beginning service on 5 September. During her second war patrol, U-978 completed the longest underwater Schnorchel patrol of World War II, lasting 68 days. The record-breaking patrol began on 9 October 1944 when she left Bergen, Norway and ended on 16 December when she returned to Bergen from her patrol. Note that the famed underwater patrol of GS U-977, during her surrender to Argentina, was not the longest, as sometimes stated, it lasted at most 66 days. During her two patrols U-978, did not sink any ships, but damaged one ship beyond repair, which totalled.

Fate
U-978 survived the war as did her whole crew, and was surrendered at Trondheim on 8 May 1945. She was sunk on 11 December 1945 during Operation Deadlight by torpedoes at location 55.83333°N, -10.08333°W.