British Porpoise-class submarine
The Porpoise class was an eight-boat class of diesel-electric submarines operated by the Royal Navy. This class was originally designated patrol submarines, then attack. They were the first conventional British submarines to be built after the end of World War II. Their design was, in many ways, influenced by the German World War II-era Type XXI U-boats.
HMS Rorqual
Type XXI submarines were a class of German diesel–electric Elektroboot submarines designed during the Second World War. One hundred and eighteen were completed, with four being combat-ready. During the war only two were put into active service and went on patrols, but these were not used in combat.
U-2540 in wartime configuration and exhibited at the Maritime Museum in Bremerhaven. It is the only floating example of a Type XXI U-boat.
Construction consisted of nine prefabricated sections
U.S. Navy diagram of a Type XXI U-boat. Note the teardrop-shaped fairing for the large hydrophone array beneath the bow and the wasp-waist pressure hull. The large sonar array and its housing did slow the boat down, but its placement and size allowed for a very sensitive system to be installed, and gave it near-360 degree coverage around the submarine.
Three Type XXI U-boats and one Type VII U-boat moored at Bergen, Norway (May 1945). The Type XXI in the middle is U-2511
