World War II Aircraft Carrying Japanese Submarine Discovered 2,300 Feet Off Oahu Coast [VIDEO]

A Japanese mega-submarine that went 'missing' during the World War II has finally been located by a team of explorers off the Oahu coast.

The 400-feet, WWII era Imperial Japanese Navy mega-submarine - I-400 that went missing since the 1946, after it was deliberately scuttled by the U.S. forces has finally been traced in more than 2,300 feet of water off the southwest coast of Oahu. This discovery was led by undersea explorer Terry Kerby at the Hawaiʻi Undersea Research Laboratory (HURL).

This new discovery of I-400 called the Sen-Toku, solves the long lying Cold War mystery of where the lost submarine was present. This discovery was made in collaboration with NOAA archaeologists Drs. James Delgado and Hans Van Tilburg.

"The I-400 has been on our 'to-find' list for some time. It was the first of its kind of only three built, so it is a unique and very historic submarine," Kerby said in a statement. "Finding it where we did was totally unexpected. All our research pointed to it being further out to sea. The multi-beam anomalies that appear on a bottom survey chart can be anything from wrecks to rocks-you don't know until you go there. Jim and Hans and I knew we were approaching what looked like a large wreck on our sonar. It was a thrill when the view of a giant submarine appeared out of the darkness."

Until the 1960s, the Sen-Toku class of submarines was the largest submarines ever built. What is interesting about these large submarines is that they had a range of 37,500 miles. I-400 along with its sister ship I-401 could travel more than one and half times around the world without the need to refuel. This high capacity is absent in other diesel-electric submarines.

As a part of the National Oceanic and Atmospheric Administration's (NOAA) maritime heritage research effort,  HURL has made use of the unmanned submersibles Pisces IV and V to look for submarines and other cultural resources. They looked for heritage properties that offered information of the past. The I-400 that was newly discovered is an aircraft-carrying submarine similar to I-401. The two have a three folding wing float plane bomber that can be launched with catapult once the submarines are surfaced. Each of the two can carry almost 1,800 pound bomb to attack the U.S. mainland. But their mission was limited.

"The innovation of air strike capability from long-range submarines represented a tactical change in submarine doctrine," said Delgado, director of NOAA's Maritime Heritage Program, within the Office of National Marine Sanctuaries, Washington, D.C. "The large I-400, with its extended range and ability to launch three M6A1 Seiran strike aircraft, was clearly an important step in the evolution of submarine design. The I-400 is technologically significant due to the design features associated with its large watertight hangar. Following World War II, submarine experimentation and design changes would continue in this direction, eventually leading to ballistic missile launching capabilities for U.S. submarines at the advent of the nuclear era."

The U.S. Navy had seized five Japanese submarines, including of which I-400. They captured subs were brought to the Pearl Harbour where inspections were conducted when the Soviet Union demanded access to them in 1946, the subs were sunk off the coast of Oahu.The wreck was identified using side scan sonar and multi beam sonar data to identify the abnormality on the deep sea floor filled with debris. Based on the features of the debris the team identified the wreck as I-400.