FL-boat

The FL-boat (Fernlenkboote, 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 kg 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 driven by internal combustion engines, and controlled remotely from a shore station through several miles of wire wound on a spool on the boat. An aircraft was used to signal directions to the shore station. They could attain speeds of 30 knots. They were constructed by Siemens-Schuckertwerke.

On 1 March 1917 an FL-boat hit the Nieuwpoort mole and on 28 October 1917 one hit the Royal Navy monitor HMS Erebus.