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Why Cold Water is Dangerous

Cold Shock and Swimming Failure

Can Cause You To Drown In A Matter Of Seconds 

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"Many people who are classed as "good" swimmers appear to be unable to swim distances of as little as 6-10 feet (2-3 meters) in cold water, even to save their lives." 

- Golden & Tipton, Essentials of Sea Survival (2002)

Cold Water Can Kill You Within Seconds

Sudden Drowning

Few people realize that water between 50-60F (10-15.5C) can kill you in less than a minute. It's actually so dangerous that it kills a lot of people within seconds. Not because of hypothermia or incapacitation, but rather because of cold shock and swimming failure.


Thousands of people have drowned after falling into cold water and a lot of them died before they even had a chance to reach the surface - because if you gasp when your head is under water, you'll drown.

These are scientific and medical facts that most people have trouble appreciating - because they have no experience being in really cold water.

Many people also drown within a couple of minutes because their arms become too cold to continue swimming and they aren't wearing a lifejacket.  


Cold Shock, Swimming Failure

& Incapacitation

This 9-minute video explains why cold shock, swimming failure, and incapacitation frequently result in rapid drowning – even for people who are considered good swimmers.

Why people don't think cold water is dangerous.

First: Because it doesn't look dangerous at all. In fact, if it was a predator, we'd say that it was perfectly camouflaged.

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Second: Because they mentally compare it to cold air and reach a completely mistaken conclusion: That there isn't any difference between cold air and cold water. 

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It's a very easy mistake to make, and it gets a lot of people killed each year.  Because when it comes to cold stress, water is very different than air. Here's why:

Water Feels Colder Than Air

For example, 45F (7C) air feels cold, but 45F (7C) water feels like it's burning your skin.  Why is that?  It's because water has much greater density than air, so it conducts heat away from your body much faster. Here's an example of how density affects the way a cold object feels: 


The Hammer Test

Let's say you forgot a hammer on your back porch and it's 35F (1.6C) outside. The hammer has a wooden handle and a steel head. When you go outside and pick it up, the handle certainly feels a little cold, but not nearly as cold as the steel. In fact, if it's minus 5F (-20C), you can pick that hammer up by the handle with your bare hands, but if you touch the steel, your skin may instantly freeze to it.  So density is why water feels so much colder than air.  It's also why your body responds very differently to 50F (10C) air than it does to 50F (10C) water.

Sudden Drowning

With very few exceptions, immersion in cold water is immediately life-threatening for anyone not wearing thermal protection like a wetsuit or drysuit.


When cold water makes contact with your skin, cold shock causes an immediate loss of breathing control. The result is a very high risk of suddenly drowning - even if the water is calm and you know how to swim. The danger is even greater if the water is rough. In rough water, inability to coordinate your breathing with wave splash greatly increases the danger of inhaling water. 

Gradual Drowning

Cold water drowning can happen immediately, but it can also take a fairly long time – a gruesome, drawn-out process in which small amounts of water are inhaled, over and over again, until your lungs become so waterlogged that you suffocate. Inhaling about five ounces (150 ml) of water is enough to cause drowning.

Heart Failure and Stroke

Because skin blood vessels constrict in response to sudden cooling, cold water immersion also causes an instantaneous and massive increase in heart rate and blood pressure.  In vulnerable individuals, this greatly increases the danger of heart failure and stroke.


All of these things happen long before hypothermia becomes an issue.

If cold water is so dangerous, how do ice-water swimmers and polar bear plungers do it?  Click those links to find out.

Stage of Immersion

Stages of Immersion

Some cold water deaths happen instantly, while others take hours. Learn about the four stages of cold water immersion, what happens during each of them, and why.  These are four separate threats to your life, and they affect you in different ways, but the first three have one thing in common: they greatly increase your risk of inhaling water and drowning. Click on any highlighted link for more information.

Cold shock is the first threat to your survival.  It happens the moment that cold water makes contact with a large area of your skin.  Not just your face, for example, but more like your entire chest and back.

Incapacitation involves the progressive cooling of your muscles and nerves to the point where they simply stop working.  First they get weak, then they get weaker, and finally they don't work at all. At that point, you're just hanging helpless in the water in your life jacket, unable to move your arms and legs.  It’s quite possible to lose the ability to use your hands in 60 seconds, and use of your arms in minutes.

Hypothermia involves a drop in your deep body (core) temperature - the temperature of your brain, heart, lungs, kidneys, liver - in other words, your vital organs.


Circum-Rescue Collapse is not well understood, but appears to be related to an abrupt drop in blood pressure. It can cause unconsciousness and also heart failure.  It can occur just before rescue, during rescue – as the victim is removed from the water - and after rescue when the person is out of the water.


Key Point:  You can drown in the cold shock stage, the incapacitation stage, and the hypothermia stage, but you have to survive cold shock before incapacitation or hypothermia even become a survival issue. 

"My first experience with cold shock was as you said. I'll never forget it. Pain, gasping, and unable to move. When I finally did move and climb back in the boat, first try, I sat for quite awhile trying to collect myself from the experience.


Warm air, cold water, underdressed on top due to high aerobic paddling. My paddling partners didn't see me and kept going. I was 10 yds from shore which was no comfort with the pain I experienced.


- Jim Meehan

Note: Jim was wearing a lifejacket.

Acclimating To Cold Water

Acclimation is a process by which your body gradually adapts itself to cold water through repeated exposure.


Learn more about acclimation.

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