Boy Scout handbook has a similar deal digging a hole and using a plastic
cover with a rock in the middle and a cup underneath. All you need is
plastic to admit light (and heat)a reasonably cone shape, and something
to catch the evaporated water that condenses on the underside of the
sheet. The idea is that the sun heats the contaminated water, causing
some to evaporate, leaving the contaminants behind; The vapors then hit
the cooler plastic sheet and re-condense -- then you need to direct the
condensate and catch it in something.

Anthony Page wrote:
I am concerned with reclaiming sea water for drinking water for emergency
situations on a boat. I saw a TV show a while back where they had a tripod
with a plastic cover over it, sort of like a teepee with buckets at the
bottom ends of the tripod legs, and a bucket in the center. They put
seawater in the center bucket, the sea water would evaporate leaving the
salt in the bucket, the sides of the tripod would condensate with water and
drip down the sides to the leg buckets for drinking. Does anyone know where
to buy this or does anyone have a description on how to make one?