Thanks for the responses. I remember long ago having an orange painted foam block for...something related to an old outboard on summer holidays, I can't remember what the heck was so important to keep afloat. I just remember the dayglo floatie. It would be easy to make one.
I found this:
http://www.henrys.com/78767-NIKON-FLOATING-WRIST-STRAP-AW110.aspx
It might do the trick. I really like the clamp idea. I stash the camera all too often, out of trouble, but alas also out of reach (and thought). Being able to clamp it (and being floatable?) might result in me actually taking more pictures. Those gunwale level pics are great.
Oh, the painter idea...I like it. A 2'-3' cord attached to the thwart, camera attached to cord with carabiner? Experiments to follow...