Hitler's "unsinkable ship," the Bismarck, was deployed in 1941 to wreak havoc on Allied ships in the Atlantic, but settled on the ocean floor after just nine days at sea. NGC investigates: Who really sank the Bismarck? Explore the wreckage in brilliant HD as we break down the events leading to the ship's final naval battle. Later, hear the stories of camaraderie between British and German survivors who fought to rescue the thousands of others perishing in the deathly frigid waters.