A Nazi submarine described as an 'underwater Chernobyl' is being sunk into sand to stop deadly chemicals leaking into the sea and the surrounding bed. The wreckage of the German U-boat was left with 1,800 canisters of toxic mercury seeping into the sea off Bergen in Norway. U-864 was torpedoed by a British submarine in early 1945 as it headed for Japan carrying jet parts. The vessel left Kiel in Germany on December 5, 1944, but the hull was damaged in an attack and the captain headed for Norway to carry out repairs.