Paragon suggested tyvek, if all you are going to do is build a shelter with it the tyvek is a good choice it is about like the visquene I suggest except it is white and relatively expensive when compared to standard plastics. If it is to be used to build a solar still black or clear is best. White plastic bags or tyvek will reflect the sunlight away reducing a still's effectiveness. If it is going in a kit where room and weight is a major concern a thin plastic like a painter disposable drop sheet or large plastic trash bags. Both will do just about anything you want it to but they are thin and can rip but a small roll have a lot on it. When you use it as a solar still put a leaf or something between your center weight and the plastic to keep it from melting through. If weight and space are not an issue use clear visquene.