The I-400-class submarine Imperial Japanese Navy (IJN) submarines were the largest submarines of World War II and remained the largest ever built until the construction of nuclear ballistic missile submarines in the 1960s. The IJN called this type of submarine Sentoku type submarine . The type name was shortened to Toku-gata Sensuikan . They were submarine aircraft carriers able to carry three Aichi M6A Seiran aircraft underwater to their destinations. They were designed to surface, launch their planes, then quickly dive again before they were discovered. They also carried torpedoes for close-range combat.
I-401, with its long plane hangar and forward catapult
The Aichi M6A Seiran
Officers of I-400 in front of the plane hangar, photographed by the US Navy following the surrender of the submarine at sea, one week after the end of hostilities.
Members of the US Navy inspecting the plane hangar of I 400.
A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Submarines are referred to as boats rather than ships irrespective of their size.
US Virginia-class submarine underway in Groton, Connecticut, July 2004
Russian Akula-class submarine of the Northern Fleet, in 2008
An early submersible craft, built by Cornelis Drebbel, propelled by oars
1806 illustration by Robert Fulton showing a "plunging boat"