I was near a walmat today so I stopped in and check the 1.00 bin. There was some material that felt like nylon but was not ripstop. It ssems slightly heavier than 1.9 ripstop (going by how my 1.9 ripstop tent feels. I asked the "associate" if she knew what it was. She said no, but she thought it might be waterproof. She cut a piece off and I tested it at a water fountain. Sure enough, water just beads on it. In fact, you can get water droplets to act like mecury beads on it. If I made a bag out of it it would not leak. It is not plastic. One end was frayed like cutoff jeans get after several washings.
There was only 4 1/2 yards so I bought it for $4.50. I think it would be too heavy to make a tarp even if there was enough of it.
I'm thinking of making snake skins out of it - but I'd like some suggestions.