Hi mate,
this occurred to me many times, and i think its perfectly realistic. Once i luckily sank a destroyer this way, who had overran me from bow to stern while i was starting to crash dive. My tower and deck were razored off completely, but his belly was opened like a tin can, 30 seconds later he travelled to deep sea grounds forever while i was still afloat.
But A DESTROYED (not damaged only) tower can be manned by nobody anymore, just imagine it in a real u-boat. The tower's hatch would not open anymore, and you surely would pray that it stayed closed for the rest of the journey. Maybe you could climb up on its outside like an ape using a deck hatch, but that's something one can't expect in a game i think. (would be nice though). It's some sort of thougtless programming in the game i think, that you as a captain/player still are able to do it.
I know this hurts and really gets on a players nerve, but that's "reality"
You only could have tried to man the deck gun (if still ok), and hope that maybe you or your gunmen spot a ship from there, though chances are very small because of the low-horizon and smaller angle of sight.
I personally see it as an extra-challenge to bring my wrecked boat and shocked crew home, especially without any real sensors anymore, and never teleport in a situation like this. To me the game is not only about attacking and tonnage, i find it really challenging just to survive.
