A 122m-long Japanese World War II submarine has been discovered off the coast of Hawaii some 67 years after it went missing during a mission to attack the Panama Canal.
The vessel was identified as the I-400 Sen-Toku submarine – one of the largest pre-nuclear submarines ever built. Its sister ship, the I-401, was discovered eight years ago also near Hawaii.
Until the accidental discovery made by scientists from the University of Hawaii at Manoa during research in the waters of the Pacific Ocean, the disappearance of the I-400 had been a mystery.
"We came upon this as we were looking for other targets. It is like watching a shark at rest," said Jim Delgado, a researcher aboard the Pisces V deep-diving submersible who travelled to the wreckage.
The vessel was found lying on the rock and debris littered ocean floor about 700m beneath the surface.
"It was torpedoed, partially collapsed and had sunk at a steep angle," said Delgado, an archaeologist with the National Oceanic and Atmospheric Administration (NOAA), which helped to fund the dive.
Both, the recently discovered I-400 and its sister ship I-401 were designed to be able to travel across half of the globe without having to be refuelled and could hold up to three folding-wing bombers that could be launched minutes after resurfacing, the scientists said.
The US Navy captured five Japanese subs, including the I-400, at the end of World War II and brought them to Pearl Harbor for inspection, the scientists said on Monday.
It is believed the US forces sank the submarines but claimed not to have any information about their location, in a bid to prevent the technology falling into the hands of the Soviet Union, which had demanded the ships be returned to Japan.
Other mega subs have been found in waters off Oahu and in the Sea of Japan. One in the submarine class remains missing.
Though the latest discovery was made in August, it has only been announced on Monday after the US National and Oceanic and Atmospheric Administration (NOAA) had reviewed its findings with the US State Department and Japanese government officials, researchers said.