The wreck of a Japanese ‘mega submarine’ from the WWII era has been drawn and photographed by researchers in Hawaii. The sub is said to be so big that it includes a hangar from which it could launch floatplane bombers.

In Dec. 2013, the Imperial Japanese Navy’s l-400 model was first discovered by a team of researchers at the University of Hawaii and the United States National Oceanic and Atmospheric Administration. Researchers returned to the wreck located off the coast of Oahu as part of an ongoing project by NHK, which is the Japanese Broadcasting Corp. Their goal was to find key pieces of the l-400 for a documentary that is set to broadcast in May. The dives have allowed the researchers to map the wreck in further detail and capture video of the submarine’s aircraft hangar. The Hangar could hold three aircrafts that have the ability to propel when the submarine surfaces.

The whereabouts of the submarine had been lost until 2013 when it was rediscovered in a 2,300 feet pursuit under water. It was initially captured near the end of the war when it was deliberately sunk by the United States Navy in a body of water off Pearl Harbor. The intent in sinking the sub was to keep its innovative technology and design a secret from the Soviet Union.

‘It was the first of its kind of only three built, so it is a unique and very historic submarine,’ stated Terry Kerby, Operations Director, and Chief Submarine Pilot of Hawaii Undersea Research Laboratory.