Shinyo Suicide Motorboat

The Shinyo (震洋, "Sea Quake") were small plywood motorboats developed from 1944 as a last-ditch coastal defense weapon. The Type 1 Shinyo measured approximately 5 meters in length and displaced about 1.3 tons. Power was provided by a converted Toyota 4-ton truck engine. The bow contained 250 kg of explosives, and some models additionally carried two 120mm rocket launchers.

The first prototype was completed on 27 May 1944 and production continued until the end of the war, with approximately 6,200 boats (6,197) completed — making the Shinyo by far the most numerous Japanese special attack weapon. Nearly 4,000 were deployed operationally by the war's end.

Shinyo were organized into special attack squadrons (震洋隊) and hidden in coastal caves and tunnels (格納壕) to protect them from air attack until needed. They were deployed throughout the Pacific including the Philippines, Okinawa, Taiwan, and mainland Japan's coastline.

The Shinyo saw limited but notable combat use. In the Philippines, Shinyo based on Corregidor sank several US landing craft support ships off Mariveles in February 1945. During the Okinawa campaign they sank two more landing vessels and damaged a destroyer. However, the slow speed and vulnerability of the plywood craft meant most were destroyed by Allied countermeasures or bombed in their shelters before seeing action.