Largest non-nuclear submarine

On 1 August 2013, submariners in the submersible Pisces V belonging to the Hawaii Underwater Research Laboratory in Manoa, Honolulu, Hawaii, USA, found one of the five World War II I-400 Japanese submarines of the Sen-Toku-class that had been scuttled by US forces in 1946 off the island of Oahu. The 400-ft-long (121 m) submarine was the first of its class and had trained to attack the Panama Canal. Before the advent of nuclear submarines in the 1950s, these were the largest submarines ever built. They could carry up to three float-plane bombers underwater and circumnavigate the world one-and-a-half times without refuelling.