On June 4, 1944, two days before the allied landings in France on D-Day and well into her twelth patrol, the German submarine U-505 was captured by a US Navy anti-submarine task force in the area of the western Atlantic that lies just south of the Canary Islands.  The capture of the sub itself was a great coup, made even greater by the fact that it was captured with a functional Enigma machine on board.

From the boat’s Wikipedia entry:

All but one of U-505’s crew were rescued by the Navy task group.  The submarine was towed to Bermuda in secret and her crew was interned at a US prisoner of war camp where they were denied access to International Red Cross visits.  The Navy classified the capture as top secret and prevented its discovery by the Germans.

The sub is now a museum ship in Chicago, and THIS video, from the Travel Channel and less than three minutes in length, gives a brief tour of the boat’s interior.