Ha Ha. You might look like a halibut. The syntactic foam sounds good. I know it's been used before on subs.I have no experience with it, but I wonder if you could make/get some in a block shape, and cut it to fit.Is it expensive?Some types of foam, including styrofoam, give off toxic chemicals and/or fumes.I think pretty much everything gives off something bad when it burns.I like the idea of a floating teddy bear though. Specially with blinking eyes!I look forward to researching the links you posted when I get a little more time.Frank D.