Hehe... nice.
Thought about trying to do the background "non-SB" (using a real photograph of sea or even a computer-made picture but with multi-shade palette)?
You should make the horizon a few pixels over the hull water line to show perspective. The ship drawing itself shows no perspecitve as per the projection and orientation we use but if you were really using the same perspective as the ship for your enviroment you would not see the surface of the water at all, just a line and then an underwater profile. The scale of the ship is small enough, however, that you can get away with perspective in the enviromen. even if the ship does not have it.