I believe a set was on a boat at the start of the WaterTribe EC2014. I think I have a picture of it, but can't lay my hands on it right now. It appears to be some solid, non-porous material. Sort of a rubber-coated fabric. On an AI, I think it is nuts.
The first spray skirts I had on my AI were given to me. They were made by a friend who installed them on my boat during a camping trip. The material was mesh, but not very porous. The first time that my bow dove, it scared me. It seemed like it was never going to come back up. The second time, I was only a little less nervous. I took them off and never used them again. The 70% shade cloth which KB recommends, and I have used, is excellent. You can see mine at http://www.hobiecat.com/forums/viewtopic.php?f=70&t=7276&start=285