 The service was the only ever railway ferry service on a lake in Norway, and SF "Ammonia" is the only remaining railway ferry steam ship in the world.In 1944, during World War II, SF Hydro was the target of the Norwegian heavy water sabotage, when the ferry was sunk to 430 meters deep in Lake Tinn to prevent Nazi Germany from developing nuclear weapons.In 1929 Norsk Hydro also establish itself at Herøya in Porsgrunn, and in 1991 the factory in Rjukan, and therefore also the railway line, was closed.