Can you drink seawater? | QuenchSea

Can you drink seawater? | QuenchSea

Can you drink seawater? If not, why not?

Water, water, everywhere… Covering over two thirds of our planet’s surface, the ocean feels almost infinite. We’ve yet to explore over 80 percent of its mysterious briny depths, home to creatures beyond our imagination.

It’s no wonder that these vast expanses of water have fascinated humans for millennia — the lure of shimmering waters and adventure on the high seas endures to this day. Our ocean and craggy coastlines are some of the few unpopulated places left where we can reconnect with nature. 

Exploring the great outdoors comes with its risks however — even the most experienced sailor or trail-hardened hiker can end up stranded and at the mercy of the elements with a dwindling water supply. So what happens then? Although you’re surrounded by the stuff, as the saying goes, you can’t drink a drop of it.

Why can’t you drink seawater?

Drinkable water is second only to breathable air when it comes to basic human survival, so accessing it literally means the difference between life and death. 

If you’ve ever inadvertently gotten a mouthful or noseful of water while taking a dip in the ocean, you’ll agree that swallowing it is the last thing you want to do. Besides the terrible taste, the salt-loaded liquid is toxic to humans. 


Unlike marine creatures, such as seals and penguins, whose super efficient kidneys or nasal glands remove excessive levels of sodium from their blood, humans are not designed to drink seawater. 

Our kidneys filter out excess salt in the bloodstream by pulling all the available freshwater from our cells and then producing urine. However, since seawater has around four times the salt content of blood — 35 grams per litre compared to blood’s 9 grams per litre — our bodies quickly run out of the fresh water needed to expel all that sodium. In other words, if you swallowed some seawater you’d have to urinate more water than you drank to get rid of all the extra salt. 

Symptoms of salt water poisoning

When the human body is unable to get rid of the salt ingested via seawater it quickly becomes dehydrated and can experience the following symptoms before dying: 

  • Vomiting
  • Dizziness
  • Delirium and hallucination
  • Increased blood pressure and thickening of the blood
  • Kidney failure 
  • Coma

And the salt’s not the only issue, bacteria, larvae, plankton and worms found in seawater can also make you severely ill.

Can you turn seawater into drinkable water?

It is possible to turn seawater into water that’s safe to drink — this process is called desalination — but there’s quite a bit of flimflam surrounding the methods used to do so. 

Let’s start by debunking a few of the myths floating around. 

Can you drink boiled seawater? 

No. Boiling seawater does not make it safe to drink because it doesn’t remove the salt. 

Freshwater on the other hand - say from a river - can be boiled to make it safe enough to drink. If the freshwater’s cloudy, you should let it settle and filter it through a clean cloth or coffee filter before bringing it to a rolling boil for at least one minute. According to the World Health Organisation (WHO), heating water to a temperature of 70°C will kill 99.999% of bacteria, pathogens, protozoa, and viruses. Since water boils at 100°C you’ll be able to tell when it’s safe to drink without using a thermometer.

Does filtering seawater through cloth make it safe to drink? 

No. Although filtering water through a clean filter can remove some small particles, the individual sodium and chloride ions — which make up the salt dissolved in the water — are very small and will pass through the filter.



In order to safely desalinate seawater you need to use a process of either distillation or reverse osmosis.

Though these methods are very effective, desalinating saline water is costly for us and the planet. Both distillation and reverse osmosis techniques require infrastructure and a great deal of energy — usually in the form of fossil fuels — which are expensive and leave a large carbon footprint.



One of the most well-known techniques used to obtain safe drinking water is through distillation. You can safely drink the salt-free water vapor collected when you boil seawater. 

If your only heat source is the sun then you can use a plastic bag or bottle placed over some seawater and catch the drops of condensation that evaporate. The process is quite tricky and time-consuming though.

Reverse osmosis

Reverse osmosis is where seawater is forced through a very fine semi-permeable polymer membrane (essentially a filter) at high pressure. The membrane contains holes about a fifth of a nanometre in size — a nanometre is a billionth of a metre — so it allows water molecules to pass through but prevents salt, chemicals, and any other impurities dissolved in the water from getting to the other side.

QuenchSea portable desalination device

Until now, there hasn’t been an easy method of accessing drinkable water if you find yourself stranded at sea or on the coast. QuenchSea is a groundbreaking, low-cost, portable desalination device that lets you instantly turn seawater into drinkable fresh water in the worst case scenario. 

QuenchSea has an inbuilt ultrafiltration and micro-filtration system to remove suspended solids, bacteria, viruses, parasites and micro-plastics, and has been aggressively tested in Dubai using water from the Persian Gulf which has one of the highest salinity rates in the world.

The QuenchSea device can produce up to 6 litres of water per hour and doesn’t require batteries as the hand-operated lever generates energy using a unique hydraulic system. This is a vital lifeline for adventure seekers everywhere.

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