German submarine U-681 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. The submarine was laid down on 12 October 1942 at the Howaldtswerke yard at Hamburg, launched on 20 November 1943, and commissioned on 3 February 1944 under the command of Oberleutnant zur See d.R. Helmut Bach.
Attached to 31st U-boat Flotilla based at Kiel, U-681 completed her training period on 31 October 1944 and was assigned to front-line service.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-681 had a displacement of 769t when at the surface and 871t while submerged. She had a total length of 67.1m (220.1feet), a pressure hull length of 50.5m (165.7feet), a beam of 6.2m (20.3feet), a height of 9.6m (31.5feet), and a draught of 4.74m (15.55feet). The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of NaNPS for use while surfaced, two Siemens-Schuckert GU 343/38–8 double-acting electric motors producing a total of 750PS for use while submerged. She had two shafts and two 1.23abbr=onNaNabbr=on propellers. The boat was capable of operating at depths of up to .
The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, the boat could operate for at ; when surfaced, she could travel at . U-681 was fitted with five 53.30NaN0 torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.82NaN2 SK C/35 naval gun, (220 rounds), one 3.7cm (01.5inches) Flak M42 and two twin 2sp=usNaNsp=us C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.
On 10 March 1945, U-681 grounded off Scilly, damaging the pressure hull and propellers. Unable to dive, Werner Gebauer, the commander of the U-boat, headed for the Irish coast, hoping for internment by Irish authorities. However, the next morning PB4Y-1 Liberator N of VPB-103 spotted U-681 on the surface and went in for the attack. Eight depth charges further damaged the U-boat, and Gebauer ordered the crew to abandon ship. With sea cocks opened and demolition charges set, U-681 submerged followed by a massive explosion. Of the crew of 47, a British escort picked up 38 survivors.