World War II saw the greatest ever loss of ships and lives at sea. As we drain the oceans, each vessel tells its tale: From the Arizona in Pearl Harbour, to Nazi super-ship the Bismarck, flaming merchant ships torpedoed by U-boats off tourist beaches of the US, to the Allies’ costly D-Day beachhead and the troopship Leopoldville sunk with the unexpected loss of 800 American lives.