5. Japanese I-400 Mega-Submarine
It was in 2013 that there was a discovery made of a Japanese mega-submarine off the coast of Oahu, a Hawaiian Island. This mega-sub was an I-400 which was the biggest submarine that was used by anyone during the Second World War. And they were able to carry up to 3 Aichi M6A1 Seiran floatplanes. These mega-submarines had been initially developed in order to be able to surface, have their planes launched and then dive back down again quickly before they were spotted.
They did, of course, carry torpedoes in case of close combat and they were the catalyst for the leading submarines that are used across the world today. It was on the 30th of December 1944 that these submarines were first launched. It was in April of 1945 that the Japanese had been getting ready for a Panama Canal strike whereby the Japanese would destroy all of the locks in the canal.
But once Okinawa had fallen, this attack had to be canceled and the fleet subsequently turned their attention towards attacking a total of 15 United States aircraft carriers that had gathered at the Ulithi atoll. Before this attack could begin however the Japanese had surrendered on the 15th of August 1945 following the dropping of the atomic bombs on Hiroshima and Nagasaki. The United States destroyers who received the surrendered I-400 could not believe the size of this submarine.
This was brought to Hawaii by the Navy to be closely inspected by their team in order to glean secrets as to how it was constructed. They had a number of different Japanese submarines that they were inspecting here but when they got worked that there were soviets being sent to conduct their own inspections on them, the decision was taken to scuttle them before they could carry out these observations. It was on the 4th of June 1946 that I was scuttled by the USS Trumpetfish near Oahu, Hawaii where it remained for another 70 years before being discovered.