Launched in May 1903 as 'Torpedo Boat No.150', the Delfin was the Russian Navy's first effective submarine, and also one of the first submarines in the world to see active service. With its single hull and petrol/electric propulsion Minonoska 150 (the name Delfin was not given until May 1904) was similar in size and concept to the U.S. Navy's Holland-type submarines which had begun to enter service a few years earlier. The vessel's designers also borrowed ideas from a number of other sources and developed several of their own, creating a truly innovative marine weapon. Displacing 113 tonnes surfaced, 123 tonnes submerged and with a length of 19.6m, beam 3.6m, she was powered by a 12-cylinder Panhard-Levassor petrol engine giving 300h.p. She had a surface range of 243 miles at speed of 8.5 knots, and 35 miles at 4.5 knots submerged powered from her 120h.p. Siemens electric motors, and an armament of two 38cm. torpedoes and one Maxim machine gun with a crew of two officers and eleven men.
In 1904, whilst in use as a training vessel before she was officially commissioned, the Delphin suffered a disaster when she sank during a stationary practice dive, drowning most of the crew. However, in November 1904, with the war in the Far East going very badly for Russia, the reconstructed vessel became operational in February 1905 and made her first sea outing on 13-16 March. In mid-April the Delfin made a nine-day foray down the coast of Korea as far as Wonsan looking for Japanese troop transports: probably the first combat patrol ever made by a submarine and an impressive feat of endurance for such a tiny, primitive, overcrowded vessel. Two other patrols followed, but on 5th May 1905 she sank in dock at Vladivostok following an explosion of petrol vapour and hydrogen from the batteries. The wreck was raised and repaired but was not re-commissioned until November 1905, by which time the war with Japan was over. The Delfin served the rest of her career as a training boat for the Siberian submarine flotilla at Vladivostok until October 1916 when she was transported by rail to the Arctic port of Murmansk to be used for local defence against possible raids by German cruisers. On arrival the boat was found to be too old fashioned and in too bad a state of repair even for harbour defence, and was thus abandoned until she finally sank at her moorings in September 1917. The hulk was later raised and used as a floating pontoon by the Soviet Navy before being scrapped in 1932.