 Verksted on 19 July 1913 on a bid of NOK 268,000; in the end the cost was NOK 334,293.It was launched on 10 December 1914, but rebuilt and relaunched on 5 June 1915 as the original configuration used too much coal.In 1929 "Hydro" was supplemented with a third ship, SF "Ammonia"; all three operated the route until the sinking of "Hydro".