Control
The problem with this game, as I can see it, is simple. A lack of control moving left to right. Even after a dead stop is achieved, I had major problems having it begin to move straight or in the other direction. A better understanding of how a boat moves would benefit this game heavily.
In addition, the use of a sea mine in a dock is just seems silly. It seems to me you could have picked a buoy, or a post, or anything really. It just seemed like an excuse to make you explode.
All in all, not a bad game, but frankly, not one I would play again.