Can I Drink Seawater?

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Can I drink seawater?

The short answer is:  You can drink a little without harm from dehydration, but not a lot.  And you may not like all the bacteria and similar things that are in it.  Read on to understand both issues.


Our bodies tightly control the amount of salt in our blood. If the salinity (saltiness) of your blood gets very far from normal, various systems -- the brain, heart, muscles, etc. -- start not working correctly or failing entirely.

Seawater is about three times as salty as blood is. When you drink seawater, your body needs to get rid of the excess salt or things will start going haywire. So as the salt enters your bloodstream shortly after you drink seawater, your body needs to dilute it with water already stored in your body's cells, and then quickly flush it out through your kidneys as urine. Human kidneys can only make urine that's less salty than seawater, so they pull the extra water they need to dilute the seawater from other body tissues. So in the process of flushing it away your body uses more fresh (not salty) water than you took in when you drank the seawater.

So after drinking seawater, your body soon has less water in it than it did before. If you keep drinking seawater, your body gets more and more dehydrated as it pulls water from the cells to dissolve the extra salt and flush it out through your kidneys.

And you feel more thirsty than before.

If you have only seawater to drink, and you keep drinking it, you become more and more dehydrated and start to suffer the symptoms of that:

-- Thirst
-- Loss of appetite
-- Dry skin
-- Reduced urine volume, and it's darker than usual
-- Sleepiness

If you continue, you'll likely get:
-- Headaches
-- Dry mouth
-- Low blood pressure
-- Rapid heart rate
-- Dizzyness or fainting when you suddenly stand up

If you still keep going, it gets worse:
-- Delirium, imagining things that aren't there, etc.
-- Unconsciousness or seizures
-- Death, if you don't receive medical treatment

By the time you've lost about 15% of your body's water, it's usually fatal.

Your body normally has good reserves of water in its tissues, to make up losses from breathing, sweating, etc. So if a healthy person drinks a little seawater it's probably not going to hurt anything from a dehydration standpoint. Some authorities say an adult in good health can probably drink up to a liter of seawater a day, IF he also drinks lots of fresh water so his body can properly dilute the seawater and get it out of his body without needing to pull water from the body's cells for that.


If you're curious, you certainly can take a sip or two of seawater to see what it tastes like. BUT...

Seawater is NOT nice clean, filtered water like the water that comes from your faucet.  Ocean creatures die in it.  And then their bodies decay. They urinate and defecate in it. Runoff from the land often contains pesticides and sometimes poorly-treated waste from cities and farms. It can carry the hepatitis virus and many others. And so on. You get the idea.

If you're curious about how seawater tastes, the best place to do that experiment is well away from land, to be away from most of the sources of contamination. Better still would be to boil it first, to kill the bacteria and viruses that we now know are present in all natural seawater.

Having said all that, I've tasted seawater a few times, while out in a boat in a nearby busy harbor and while playing in the surf as a child. It just tastes like VERY salty water.

I didn't get sick from it. Divers and surfers and swimmers in the ocean occasionally get a mouthful of water, and most are fine afterwards.

So now you know that drinking a little seawater isn't something to panic over, but it's not a very good idea either. Just think of the generations of sea creatures that lived and died in it before it got to you.

If you're still curious to taste it, boil it first -- that way you'll find out what it tastes like and won't get sick from doing the experiment.

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