The Titanic hit the bottom of the ocean at about 35mph.
That ship was broken in half on the surface and the compartments that were watertight blew - imploded which made the back half of the ship look as it does.
I wonder how fast the Indianapolis hit the bottom?
It would have had many watertight compartments although I expect the guys left the ship with the hatches open to escape.
It was at night (midnight) so many of the watertight hatches would have been closed. But as badly as it was damaged a lot of bulkheads would have been blown down.