During second world war both the axis and allies did research on the opportunities to bring forward atomic weapons, and it was first after the war was over that the allied found out that the German project had a long way to go before a breakthrough. But during the war the Germans had begun to transport heavy water from Telemark to Germany, and this created concerns in the allied staffs. An action to stop the heavy water was necessary! After several actions against Rjukan they had delayed the production of heavy water, but not stopped it. The last action was launched on the 20th of February 1944 when the ferry Hydro was about to bring heavy water and production equipment to Germany. In a good planned action 8,4 kg of high explosive were put on Hydro, and when the ship had reached deep waters the explosive extra- cargo exploded. Hydro sank quickly and took with her in the deep eighteen peoples. After the war there were much discussion if the ship had heavy water onboard that was ment for Germany when she was sabotaged, or if the Germans had found other ways to transport the invaluable water to Germany. The discussion stood open until Hydro was found in the beginning of the nineties by a mini submarine. Onboard the wreck there were still the 600 kilos of heavy water, and in the time that came two barrels were salvaged from the deep. Another chapter in Norwegian war history was then settled once and for all. The wreck of Hydro rest today on a depth of 450 meters in the Tinnsjøen straight west of the Gaustadtoppen...