[Dan 550]

There are some flexible, semi-pourous sheet plastics that would hold the air and let some out for cushioning and the ability to use the pump constantly. But if you're really going for a simple, easy, cheap, light skirt that works, go with two layers of vynl tarp with evenly spaced holes along the nbottoms of each layer, making sure that the holes are not directly above one another so that you get maximum air cushion. Personally, I like the tarp, because it's cheap and easy to replace when torn.