Scientists searching in the Pacific Ocean off the Hawaii coast have found a World War Two era Japanese submarine that had been preparing to attack the Panama Canal before being stopped by the U.S., according to Reuters.

The 400-foot "Sen-Toku" class sub is one of the largest pre-nuclear submarines ever built, and was found in August off the southwest coast of Oahu.

Scientist at the University of Hawaii at Manoa confirmed the vessel had been missing since 1946.

The I-400 and its sister ship, the I-401, which was found off Oahu back in 2005, were able to travel one and a half times around the world without needing to refuel, according to Reuters.

Both ships could hold up to three folding-wing bombers capable of launching minutes after resurfacing.

The 1-400 was discovered some 2,300 feet beneath the surface, according to Reuters.

"We came upon this as we were looking for other targets ... It is like watching a shark at rest," said Jim Delgado, an archaeologist with the National Oceanic and Atmospheric Administration (NOAA).

The U.S. Navy captured five Japanese subs, including the I-400, at the end of World War Two and brought them to Pearl Harbor to inspect them.

"It was torpedoed, partially collapsed and had sunk at a steep angle," said Delgado.

Other subs have been found in waters off Oahu and in the Sea of Japan. At least one in the submarine class remains missing, according to the scientists.

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