I like the regular divers float but eventualy the canvas around the tube starts to go so I am leaning twards the boat fender inside the tube trick.
This has been used before, I think on a few of Martin S. world record vids you can see this set up. Looks like a big orange ball on top of a regular tube.
Basically it is on of those taylor made round boat fenders. Looks like one of those bouncy toys that kids sit on and hop around. It has a heavy duty eye on one end to tie the line to. Just put the tube under the ball with the attachment eye of the ball going down then tie on the line. The tube gives you something to hold on to while breathing up or recovering and the boat fender supplies all the load. Cheap and durable though not as portable as the cute blue thing above
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