[judicial meanz]

I suspect this is a bottom collision, because the article says the boat was underway on its own power and heading into port with damage, and it was 350 miles from port and thats a long way to do a surface transit.

Lots of reasons a boat can strike something submerged. It may be a submerged object that is floating on the currents, or they may have struck the ocean floor in a shallow area.

Depending on the speed, the sonar may or may not be useful.

[Robert A Cook PE]

And, it could have simply ran right through an 80 ton blue whale at 20+ knots.....

Not quite running aground, but the effect is similar to hitting a truck at high speed.

(Don't worry too much about the ballast tanks being bent or damaged, as far as keeping the ship afloat. If the "running aground" occurred at any angle at all, then only the bottom is bent/torn up/damaged, and the sub ballast tanks are open to sea water anyway all the time.

If the sonar dome hit, and it almost certainly did, then it's destroyed, but again, the structural integrity of the fiberglass sonar dome isn't affecting the structural integrity of the ballast tanks (which are behind the sonar dome.) If the sonar dome and sonar mounting structure (the HY-80 sphere itself that is inside the fiberglass sonar dome) were damaged, or even torn off, then there is a watertight door that isolates the sonar sphere and its electronics and trans