German submarine Wilhelm Bauer (originally designated U-2540) is a Type XXI U-boat of Nazi Germany's navy (Kriegsmarine), completed shortly before the end of World War II. It was scuttled at the end of the war, having never gone on patrol. In 1957, it was raised from the seabed off Flensburg Firth, refurbished, and recommissioned for use by the West-German Bundesmarine in 1960. Finally retired fully in 1983, it is the only floating example of a Type XXI U-boat. It has been modified to appear in wartime configuration and exhibited at the German Maritime Museum in Bremerhaven, Germany. Design Like all Type XXI U-boats, U-2540 had a displacement of when at the surface and while submerged. She had a total length of , a beam of , and a draught of . The submarine was powered by two MAN SE supercharged six-cylinder M6V40/46KBB diesel engines each providing , two Siemens-Schuckert GU365/30 double-acting electric motors each providing , and two Siemens-Schuckert silent running GV232/28 electric motors each providing . The submarine had a maximum surface speed of and a submerged speed of . When running on silent motors the boat could operate at a speed of . When submerged, the boat could operate at for ; when surfaced, she could travel at . U-2540 was fitted with six torpedo tubes in the bow and four C/30 anti-aircraft guns. She could carry twenty-three torpedoes or seventeen torpedoes and twelve mines. The complement was five officers and fifty-two men. Construction and wartime service Construction of U-2540 began on 28 October 1944 by Blohm & Voss in Hamburg-Finkenwerder. She was launched on 13 January 1945 and commissioned on 24 February 1945 as part of the 31st U-boat Flotilla for training purposes. In April 1945 the boat went to the front after training at Rønne on Bornholm. Due to the ongoing fuel shortages at the end of the war, the boat was relocated to Swinemünde before being scuttled near the Flensburg lightship on 4 May 1945. Salvage, refit and new service In June 1957, after more than 12 years on the floor of the Baltic Sea, U-2540 was raised and overhauled at Howaldtswerke, Kiel. The submarine was commissioned as a research vessel in the Bundesmarine, serving from 1 September 1960 until 28 August 1968 as a test boat (class 241). On relaunch she was renamed Wilhelm Bauer, after the designer of the first German U-boat, Brandtaucher,