Put ocean water or a solution of salt water in a small plastic container, and set it on a large saucer. Roll a blotter or paper toweling, put rubber bands around the roll, and stand it in the salt water. Cover the small container with a larger clear plastic container, and place the whole thing in the sun. When water collects on the sides of the larger container, tilt it carefully, and collect the water in the saucer. Taste the water.

This is one method used to extract pure water from ocean water.

Here's another method:

Put some ocean water or a saturated solution of salt in a flat pan. Set the pan in a warm room until the water has evaporated.

Neither of these methods would be fast enough for really thirsty people! How else could it be done?