Dive discovers missing aircraft hangar of sunken WW II-era Japanese submarine

The recent survey, the first to return to I-400 submarine since its discovery, successfully located, mapped, and captured on video for the first time not only the submarine's hangar and conning tower (navigation platform), but an unexpected and significant new discovery -- the submarine's bell. Torn from the submarine by the explosive forces that broke apart and sank I-400, the bell lies close to the conning tower on the seafloor.

The massive aircraft hangar, large enough to launch three float-plane bombers, was the defining feature of the I-400. After the end of the war, the I-400 was deliberately sunk at sea outside of Pearl Harbor to keep its technological innovations safe from the Soviet Union.

"We didn't have detailed enough bottom mapping data to help locate the hangar, conning tower, and other signature features missing from the wreck of the I-400," said Terry Kerby, operations director and chief submarine pilot of the Hawai'i Undersea Research Laboratory (HURL). "With only one dive day to try to find anything, we knew there was a strong chance we might spend the dive looking at the barren sandy bottom."

Kerby continued: "We made a lucky guess where to start when we approached the main hull of the I-400 from the northwest. Our guess started to pay off when the giant hangar door came into view, followed by the conning tower and hangar. Many items were amazingly intact for something that had ripped out of the hull of a sinking 400-foot-long submarine."

Video of initial sighting: https://www.youtube.com/watch?v=wmjmPHNYXO8