Fun game! I won my first game and thought maybe the game was too easy but I had another couple of go's and never won again so I think its plenty difficult enough - I think I just got lucky with finding a lot of fish early in the first game, haha.
The controls screen was a little overwhelming when I first opened it but the game explains itself well and it isn't too complex - after one run people should "get" it. One thing I think would be good is a keyboard shortcut for switching between move, scan, and fire.
One thing I didn't get was the hint tiles. For example, the island hint seems to cover both islands and sandbars (and barrel is supplies or bomb) so it didn't seem useful to me. At least you know its not clear water but is that useful information to know?
Game looks and sounds great too.