How to Desalinate Seawater When Stranded on a Desert Island

Odds are more than likely that you will never find yourself stranded on a desert island. Yet the scenario is one that engages the imagination of many. In case you ever find yourself in this situation, a supply of fresh water is critical to survival. Here are some steps and ideas to set up a method to desalinate seawater when stranded on a desert island.

Instructions

Difficulty: Challenging

1. Gather the materials you will need to create a desalination still. Assume that you still have the cloths off your back and perhaps a rubber raft or flotation device from the boat or airplane. You will need a large piece of smooth, water resistant material. You will need something to collect the fresh water in such as a coconut shell or bowl fashioned from raw materials such as leaves. Finally, you need something weighty enough to hold down the water resistant material.
2. Find an area of beach where dry sand meets sand that frequently gets wet. Pick out a low spot at the edge of the wet-dry sand border. Choose a spot not affected directly by the tide so that your still doesn't wash away.
3. Lay out the water resistant material flat and trace a line around it in the sand. One edge of the material should lie flush with the wet-dry sand border.
4. Make a barrier or berm around the outline of the water resistant material.
5. Dig a ditch about 2 feet inside of the outline of the water resistant material. You should dig the trench deep enough that water should begin to fill the bottom about 2 inches deep. Save the sand to form an elevated area in the center of the outline.
6. Form a pile of sand in the middle of where the outline of your water resistant material lies. This pile should be elevated above the bottom of the ditch and water in the ditch, but be significantly lower than the height of the berm, or barrier, around the ditch. This pile of sand should be about half the height of the berm around the trench.
7. Create a bowl-shaped divot in the middle of the elevated sand pile. Make the size suitable to whatever material you have to use to collect water. This indentation is where the water collector will rest.
8. Line the divot with watertight material you will use to collect the water. You may use waxy leaves or coconut shells, waterproof clothing or part of a rubber raft or flotation device.
9. Drape the large piece of water resistant material over the pit you have created with the berms, trenches and sand pile. Weigh it down on the outside edges with rocks to hold it in place. Be sure that has enough slack to droop down in the middle.
10. Weigh down the center of the large piece of material so that it hangs over the bowl shaped divot in the top of the sand pile.
11. Wait for the desalinated seawater to collect in the bowl you have made. The heat of day will trap the evaporating seawater under the water resistant material. Then as the moisture condenses, the slope of the material pulls it down toward the middle.