1944 - 1952: XE Class
The XE Class were an improved version of the X Class, with air-conditioning and extra stowage space, were designed for employment in the Far East. Spring-loaded legs made it easier for these midget submarines to rest on the seabed, and an airlock allowed a diver to leave the submarine and place limpet mines on the hulls of enemy ships.
Used in the attack on the German battleship Tirpitz. They carried a crew of four, typically a lieutenant in command, with a sub-lieutenant as deputy, an engine room artificer in charge of the mechanical side and a seaman or leading-seaman. At least one of them was qualified as a diver.
In addition to the two side charges (each of which contained two tons of amatol explosive), they carried around six 20-pound limpet mines which were attached to the target by the diver.