A friend and I dug one as a test. We were thinking about going camping on the Dry Tortugas, where you have to bring all your water in for your entire trip. (The name was a bit of a tip-off there!) My buddy said, no problem, we'll just dig a solar still on the beach, like I read about. The wheels started turning, and I thought, heck, for the sake of a little digging and some cheap plastic, why not dig a few of them and produce enough water to shower with or give away to thirsty girl campers.

We tested it on a beach in the Caribbean. It was a big sucker, about 4 feet across, right on the beach, and the inside was constantly damp. We put our catch cup in the center, stretched our plastic across with a pebble in the center to create a low point from our water to drip from, and sat back to wait for a few minutes for our first refreshing drink.

Eight hours in the 90 degree equatorial sun later, we had just about a teaspoon of pure water in our reservoir. Looks like if we ever do get to the Dry Tortugas, we'll be lugging water in.