FL-boat
The FL-boat (Fernlenkboot, literally "remote controlled boat") was a weapon used by the Imperial German Navy during World War I. It was a remote-controlled motorboat, 17 m long, carrying 700 kilograms (1,500 lb) of explosives, which was intended to be steered directly at its targets - initially the Royal Navy monitors operating off the coast of Flanders. FL-boats were constructed by Siemens-Schuckertwerke.