There have been a number of 21-inch (53.3cm) torpedoes in service with the Royal Navy of the United Kingdom.
Mark VIII torpedoes being loaded onto the Polish Navy submarine ORP Sokół.
A Mark IX torpedo undergoing maintenance while loaded in a destroyer's triple tube mounting.
A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, such a device was called an automotive, automobile, locomotive, or fish torpedo; colloquially a fish. The term torpedo originally applied to a variety of devices, most of which would today be called mines. From about 1900, torpedo has been used strictly to designate a self-propelled underwater explosive device.
Bliss–Leavitt Mark 8 torpedo
Fulton's torpedo
Confederates laying naval mines in Charleston Harbor
NMS Rândunica