neat idea paul,

i'd like to see the foam, i gues it'd have to be open celled, sorta reminds me of those tiny tiny kids toys that swell up huge when dropped in the water.

but that brings up another idea. like a paddle float gives a moment only in the up direction from it's floatation, but theres little mass. And others have written about buckets or bags w/ water in them to counter act in the other direction. But they are awkward and difficult and probably impossible to set up.

but say we had a typical bozo paddle float(or any of the other floats i/ve been talking abt - but whatever) and it had a tight rolled netting pocket on one side but is was quick release opening. and in the pocket was some real open celled foam or sponge or the type you mentioned or even my yak sponge but rolled up tightly w/the netting.

so after inflating and attaching paddle float, pull the quick release on the pocket and in a few secs get a hvy mass (and profile too i guess) resist working in the opposite direction to the float.

2x the effect for a tiny bit more space.

-sounds cool

-mick