Just ran across these. Definitely not a whitewater boat but the weight is impressive, and the price quite reasonable if they sport any kind of durability. Not sure what the material is though. I’m reluctant to haul 7lbs of extra gear up to backcountry lakes to fish but I would be inclined to bring something like this along on a short trip. Could be handy for crossings too.
http://flyweightdesigns.com/products.aspx
This guy did a good write-up on the boat: http://lightweightoutdoors.com/?p=1154