These special dive suits were designed for the Japanese Special Attack Units to fend off an invasion of the Home islands by Allied forces. The suits were armed with a mine containing 33 pounds (15 kg) of explosives attached to a 16 foot (5 meter) bamboo pole.
The divers, weighed down by 20 pounds (9 kg) of lead, would walk underwater for as much as six hours and at depths of 16-23 feet (5-7 meters). The divers, upon reaching the hull of an enemy ship, would detonate the explosives, killing themselves in the process. It's not known if this suit was ever used in combat, but there are accounts of U.S. infantry landing craft and a surveyor ship being attacked by suicide swimmers.