USS Arkansas (BB-33) was the second ship in the Wyoming class of dreadnought battleships. Laid down in 1910, she saw action in both World Wars, before being assigned to the Operation Crossroads nuclear tests in 1946. While she survived the first test (Able), the Baker test sank her on July 25, 1946. The force of the underwater detonation crumpled her hull causing the accordion-like appearance you see in the image. This shot was taken whilst my buddy was investigating the 12 inch bow guns.
As an aside, just after this, I noticed the leak alarm going off inside my housing. There's nothing like having 20 minutes of decompression time while your dome port is filling up to keep an underwater photographer on his toes!
Olympus EM5, Panasonic 8mm Fisheye, 1/40s @ f3.5, ISO 3200