I saw this documentary on the Bismark were they found the ship wreck and had the three remaining German sailors that are still alive explain their side of the story and what happened as well as some of the British sailors and their side of the story. That was a very interesting show.
The Bismark was at the top and was almost unsinkable. It had some of the largest guns to date on a battleship and it had an inner wall that when a torpedo hit and penetrated the outer hull, huge flow pumps would kick in and fill the “cavity” between the outer and inner walls with sea water so fast that the torpedo would be “stopped” by the water and not allowed to actually detonate on the inner wall and therefore becoming a “dud”. The only reason it was actually sunk was due to a one in a million shot from a topedo plane that actually caught the rudder and jammed it forcing the Bismark into a circle pattern as they could not unjam it. The British fleet moved in and shelled it steady for several hours and it would not sink. The Germans said they actually scuttlled (sunk) their own ship so as to not fall into enemy hands.