U-Boat

A U-Boat (German: Untersee Boot) is the familiar name in the War for a German submarine. Over 200 are stated to have been sunk, 178 being recorded as having met their fate in action with British craft of various kinds. Over 3,000 men of the German crews went down in the U-Boats. According to official records [at the time of this publication in 1925] 15,313 persons, passengers and crews of Mercantile Marine vessels, lost their lives in the war as victims of U-Boats.

A commonly used phrase to describe the German U-Boat was Tin Pirate.