71% of the earth is covered in water, but only 2% of that water is pure.

As clean drinking water becomes more scarce,

you may be wondering what happens if I drink seawater.

Let's first examine how our bodies absorb water.

You may remember the process of osmosis where water moves from

a less concentrated solution to a more concentrated solution through a semipermeable membrane.

The cell's membrane allows water to pass through, but not the particles dissolved in water like salt.

Normally the saltiness of water inside ourselves is the same as the saltiness outside ourselves.

When you drink water, a concentration difference takes place.

Water from the outside of your cell moves inside to maintain balance.

This is called an isotonic state.

When you drink too much seawater, the saltiness outside your cells will increase rapidly

and the cells force water molecules out in order to restore balance.

So, even if you are already dehydrated, drinking seawater will cause your cells to release more water

and you will end up peeing out more liquid than you take in.

Conversely, if you chug a massive amount of pure water, the exact opposite will happen.

The saltiness outside your cells will decrease rapidly and water will be forced into your cells.

This can cause cells to swell and burst which in extreme cases leads to seizures, coma, and sometimes death.

So what can you do if you are stranded on a deserted island with absolutely no fresh water around?

The simplest way to extract fresh clean water from the ocean

is through distillation which separates the salt from the water.

In order to distill water, you must heat the seawater so it evaporates.

Then trap the evaporated water vapor until it cools and condenses back into liquid water.

Kind of like the moisture on your bathroom mirror after a hot shower.

This condense water will be free of all salt and be 100% safe to drink.

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