A book on making camping equipment had an idea for making self inflating air mattresses, which I think can be extended to make self inflating paddle floats, or flaotation bags. Unfortunately I can not remember the title or author of this book, so I regret not being able to give them credit.

The plan for the air mattresses: take a regular air mattress, cut it open, stuff very loosely with a very light foam rubber, and then reseal the seams you opened.

To inflate the air mattress you just had to open the valve. the foam would swell and as it did so, air would rush inside the air mattress. Once the valve was closed the mattress would be about 60%-80% filled, which would be just fine for an air mattress.

To pack the air mattress you opened the valve again and rolled it up.

Since the foam is very light duty it collapses very easily when pressure is placed on it, and the trapped air whooshes out.

The foam provided no actual cushioning to the sleeper, it only served to force open the mattress once the valve was opened and air could enter.

The same procedure can be used for inflating anything else. You won't get any significant air pressure, but you will get a lot of trapped air volume, which equals flotation with no cost, and the process is easily reversible and repeatable.

Make or buy a paddle float, cut it open and put in some large pieces of lightweight foam rubber. The cheapest you can find is probably best. Open cell is as good as closed cell -- and may be better. Reseal the paddle float.

To inflate the paddle float, open air intake. If you want the thing to be inflated more, puff in a few breaths. To use it, seal the inflating tube. To store it, roll it up so the faom compresses inside as the air is forced out.

Hope this helps.

PGJ