Very nice. I agree that some ripples around the fins and hull would be the icing on the cake. Nice transparency to the water, BTW. As for improving, of course! And remember, not all improvements show up in the artwork. Several images down the road you'll use a technique you used before, in a different way, with better results. And unless you're selling, you are the best judge of what you did. If you like it, SO BE IT. If others do also, even better. Don't stop, and post the next one that you're proud of!