re: Any sub experts out there?
Well I don't know that I would pin an 'expert' button on my lapel, but I worked at a shipyard that built nuclear subs and my father was a hull inspector for the the Navy Bureau of Ships for a lot of years prior to his death. The sonar dome is largely air, it's a dome so they can mount transponders all round the sphere to collect data from different directions as an aide to pinpointing its origin. The mere fact that the vessel maintained its 'watertightness', especially at that depth (700 feet?) means that most of the damage is to area(s) outside the pressure hull.