Within the "Dune" universe, a Stillsuit is a full-body suit worn on desert planets like Arrakis designed to capture the body's moisture. It consisted of various layers that would absorb then purify the body's moisture through sweating and urination. The sweat and urine would be filtered into pure water so that the person wearing the Stillsuit could drink the reclaimed water from a tube on the neck of the suit. The Fremen, the indigenous inhabitants of Arrakis, were supposedly the best manufacturers of the Stillsuit. They produced a Stillsuit so good that only a thimbleful of water would be lost per day.
If you're going to be out in the desert, you should wear a stillsuit.