I built the diorama for the Mariners Museum in Newport News and used sea life to fill two empty corners. In one I used a Calypso shark that I sanded down past "waterline". In the other I made a pod of porpoises sounding by bending round sprue. I heated and bent the sprue to form the hump, which I cut and sand it down to the desired height. I made a dorsal fin from .005 styrene strip. After painting them a brown-gray, I gloss coated them. When dry, I used gloss acrylic medium gel to adhere and blend them into the water. It worked well.