German submarine U-3506
German submarine "U-3506" was a Type XXI U-boat of Nazi Germany's "Kriegsmarine" during World War II. The "Elektroboote" submarine was laid down on 14 July 1944 at the Schichau-Werke yard at Danzig, launched on 28 August 1944, and commissioned on 16 October 1944 under the command of "Kapitänleutnant" Gerhard Thäter. Design. Like all Type XXI U-boats, "U-3506" 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-3506" 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. Service history. "U-3506" undertook no war patrols, with no ships sunk or damaged, remaining as a training vessel for the duration of the war. "U-3506" was one of three Type XXI boats (along with and ) that were scuttled in the Elbe II U-boat bunker. The bunker has since been filled in with gravel, although even that did not initially deter many souvenir hunters who measured the position of open hatches and dug down to them to allow the removal of artifacts. The boat now lies beneath a car park and she and the other wrecks are completely  inaccessible. The site is located in the Free Port of Hamburg and in order to access it one must present a passport.