How to Filter Sea Water

Along with dry firewood and a makeshift shelter to protect against the elements, a source of fresh and potable water is one of the most urgent necessities in a survival situation. The human body needs water to digest food and function effectively. The most plentiful source of water on earth is the salty ocean. With sunshine, patience, some simple materials and a little elbow grease, even saline seawater can be a source of hydration.

Things You'll Need

• Sand, soil or gravel
• Clean bowl, cup or other receptacle
• Medium-sized stones
• Clean tarp, garbage bag or other large sheet of non-porous material

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Instructions

Building a Solar Still

• 1

  Find a patch of sand or soil that gets constant or near-constant direct sunlight. Dig a large, relatively shallow pit--no larger in area than your tarp or garbage bag and not much deeper than your cup or bowl.

• 2

  Seaweed retains a lot of moisture.

  Fill the pit with seaweed or soak the sand at the bottom of the pit with seawater.

• 3

  Prop your clean cup or bowl upright in the middle of the seaweed or wet sand.

• 4

  Cover the pit with the clean tarp or garbage bag. Weight the tarp or garbage bag down around the edges of the pit with the rocks.

• 5

  Place one smaller rock in the center of the tarp, directly over the cup or bowl. This rock should be large enough for the tarp to sink down slightly, but small enough that the tarp does not touch the cup or bowl.

Extracting Water

• 6

  Let the still sit in direct sunlight for several hours, allowing fresh water to evaporate from the seaweed or sand, condensing on the underside of the tarp and leaving the salt at the bottom of the pit.

• 7

  Remove the rocks and the tarp from the pit. The condensation will have run down the tarp towards the weighted center, filling the cup with clean water.

• 8

  Repeat the process as necessary.