Excellent game design! Within 30 seconds I found myself hooked, wanting to collect all the boxes. I did manage to get all 20.
So I found it interested that the buoys were not the "real" challenge. For me, steering the ship was significantly hard than just avoiding the buoys (in fact, they seemed quite sparse in the later part of the game).
Great job. If you get a chance to play and review my game I'd appreciate it!