The Type XXIII U-boat was a series of German electrically-propelled submarines in service with the Kriegsmarine for a brief period of time, from late 1944 to May 1945, with the U-2321 being the first to be commissioned. The last one to be launched was U-4712, in April 1945, with a total of 63 Type XXIII U-boats being completed out of the 280 submarines originally planned, but only six entered service. These elektroboats, as this type of German submarines were known, carried out secret operations off the British, French, and Dutch coasts, sinking only six enemy ships during their ten operational patrols. Although it was considered a very advanced submarine, by the time they were introduced Germany was already losing the war and it was too late to make a difference as the German factories and infrastructure were being leveled to the ground by Allied bombing raids.
Like the Type XXI U-boats, the Type XXIII was a double-hull design, but had a smaller power plant, which consisted of two 580-hp electric motors and one single MWM diesel engine. The battery was fitted in the space between the two hulls. It could remain underwater for a much longer period of time than conventional submarines at that time could do, and it was able to sail faster submerged than on the surface. Designed for local deployment on coastal waters, it was only about 35 m (114 ft) long and 3 m (10 ft) abeam. So, it was small and cramped and had a crew of only 16 sailors and officers.
Type: coastal attack submarine
Length: 34.7 m
Beam 3 m
Draft: 3.6 m
Displacement: 230 tons on the surface, and 250 tons submerged
Maximum speed: 22 knots submerged and 10 knots on the surface
Armament: only two 533-mm torpedoes (pre-loaded)