Just watched the "Island" episode shot off the coast of Sumatra. Well done, but I do have a question. With hollow bamboo branches, together with something to hold a decent amount of sea water as a "source" over the fire, and a piece of the plastic and a receptacle, would it not be possible to desalinate some sea water to create your own potable water?
True, alone it may not be enough to last you for months, but, combined with collected rain water, might they not generate some significant amounts to keep one hydrated?

Thanks for the great show.
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You probably could do this but with out a good sealed container and a condensing coil it would not produce much.
On a boat you can make a solar still with a bucket, a garbage bag and a cup.
I don’t like the way I have seen solar stills built on the shows. I would dig a hole and line it with some thing dark collared that would hold water like black garbage bag. Fill it with chopped up green vegetation polluted or sea water, urine whatever has moisture. Put a cup of some kind in the middle then cover it with a clear plastic bag or one of those clear survival ponchos.