Yeap, I got one of my type IX subs destroyed by destroyer's gunfire. I was pretty surprised. But the convoy lost 80% of ships so I take it as a good exchange rate ;-)
Game is really great. Only thing that's a problem for me, but I think not for many others, is that battles (at least finishing all the merchants in convoy) takes about an hour and it's a bit too long for a guy with full time work and so, and putting app into background works for a while, but over the longer period and if I start another app in the meantime - I lose the game progress and battle is not saved in any way
I've got a problem with graphics also (ships in strategic map and explosions and water splashes drawn in wrong location) when starting app (and campaign) for the second time but forcing app to close and clearing cache helps in this problem.
Anyway, game is superb. I love both strategy and tactical layer. It's great that convoy routes change in time. Ships' AI seems pretty good to me. They are firing star shells in the night, try to surprise my cruisers with torpedo attack, retreat when overwhelmed, use smoke when running away. It's not so easy to finish wounded AI warship. And I've got beaten by HMS Hood and DD, losing Admiral Hipper, DD and having a cruiser damaged. All the mechanics of tactical combat are really satysfing - for me it seems to have good balance between realistic and arcade play. And great graphics (Unity engine rocks!), ship models are so detailed.