Does a float tube like this exists?

[Majja]

While this is not rounded like a raft I think it would do exactly what you want and weighs in at only 18lbs. Have a look

[url "http://www.northforkoutdoors.com/navigator2.html"]NFO Navigator II[/url]

It is white water rated has a place for your feet and a 700lb capicity. Now the slight down side is it is a bit on the pricey side but quality materials you will always pay for.
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