<blockquote>After Japan was defeated and the vessels were captured, the Soviets demanded access to the subs. To keep that from happening, American forces transported the submarines to a location off the southwest coast of the Hawaiian island of Oahu, where they were torpedoed and sank in 1946.</blockquote>
via <a href="http://www.gizmag.com/i-400-submarine-aircraft-hangar/37248/">Submersible photographs WW2 Japanese sub's long-lost airplane hangar</a>.