keep you alive plastic bag
 

emergency water still, 1 black plastic bag, but other large polybag will do,
large water container say 3 litre bottle or bowl, put seawater into bowl or
bottle tape tie opening of bag to the water holder pull down bag say 2",
this pleat forms channel for water accumulation, and can be held in place by
ties or tape, a plastic tube could be installed into water container in
order to replenish used water.
the closed end of bag should be peg up so that sun can radiate on it and
allowing water to drain into channel. crude but may safe a life.