Russian submarine Forel

Forel (Форель, Forelle - Trout) was a midget submarine designed by Raimondo Lorenzo D’Equevilley-Montjustin and by built by Krupp in Kiel, Germany. The Forelle proved moderately successful but did not attract German naval attention. The Imperial Russian Navy purchased the boat in April 1904 for service in the Russo-Japanese War. It operated out of Vladivostok from August 1904 until it sank in an accident in 1910.

Forelle was a single-hull boat designed as an experimental craft with internal ballast and compensating tanks. She had fixed angled aft planes, and movable forward units for dive control. This boat had to be carried into action on board a surface ship and launched close to its target, as she was not fitted with a separate surface propulsion system.