If they were knocking on the hull, at least we can be fairly certain that the hull did not implode.
Could be a pop of the hull that then flooded the inside almost immediately. Would like to see failure tests of how these kinds of hulls fail.
Other subs that failed with other hull designs were pretty gruesome, like Scorpion
If they were knocking on the hull, at least we can be fairly certain that the hull did not implode.