From the department of concepts-so-simple-that-they-shock-you:
The Watercone is an ingenious device that can take salty water and turn it into fresh water using only the power of the sun. The nice thing about this device is it is bone simple, uses the sun instead of fossil fuel, and is cheap to make and easy to use.Just visit the link. Concepts this simple prove that humanity is too complex for its own good.
The Watercone is surprisingly a cone, that you place over a pan of salty water (or over a marsh, or any damp ground) leave it out in the sun, water evaporates, the condensation trickles down the side of the cone, at the end of the day you flip it over, remove the cap at the top and drink the water.