Cold Shock
If you gasp underwater, you will immediately drown
"The sudden lowering of skin temperature on immersion in cold water represents one of the most profound stimuli that the body can encounter."
- Golden and Tipton in Essentials of Sea Survival
Translation: Short of being hit by a bus or struck by lightning, cold shock is one of the biggest jolts that your body can experience.
"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.
More Than Just A Gasp
The instant cold water contacts a large area of your skin, you experience a number of potentially lethal shock responses. The first response is gasping, but as we explain below, cold shock is a lot more complicated and dangerous than just gasping for air.
These responses are intense and completely involuntary, which means they're totally out of your control. You can't wish them away any more than you can mentally control your heartbeat. Note that just putting your face or your arm in the water is not enough to cause cold shock.
A Desperate Struggle
When they're desperately struggling in the water, people often find cold shock terrifying. They're completely taken by surprise, but they know within seconds of hitting the water that they're fighting for their lives. That's why safety messages telling them not to panic aren't very useful.
Experiencing cold shock is tough enough if you're a member of an elite military unit participating in a survival exercise - but it can be completely overwhelming if you were just out having a fun time on the water.
A Very Bad Experience:
Many victims of cold shock report that it was a traumatic experience. It can obviously kill you, but it's also the kind of thing that really rattles your cage. Many survivors can't get near their boats or boards for a long time afterwards without feeling really stressed out and creepy. That's often the way your brain processes a near-death situation over which you had no control.
It's also common for survivors to have nightmares for months afterwards. In other words, suddenly winding up in the water desperately fighting for your life is something you really don't want to experience.
Life-Threatening Responses
Cold shock responses fall into three threat categories, each of which is discussed below to give you a clear and realistic view of what you're up against in an unprotected cold water immersion:
Threat 1: Loss of Breathing Control
Threat 2: Heart and Blood Pressure Problems
Threat 3: Difficulty Thinking and Acting
Threat No. 1
Loss of Breathing Control
During the first several minutes of cold shock, and often for much longer, most people find it impossible to get their breathing under control. Breathing problems include gasping, hyperventilation, difficulty holding your breath, and a scary feeling of breathlessness or suffocation.
Gasping
This isn’t just a little gasp, like the kind you’d experience if somebody jumped out of a closet and scared you. It’s a huge gasp that totally fills your lungs. You may experience several of these gasps in a row.
Sudden Drowning
If your head is underwater when you gasp, you will immediately drown, and without the support of a lifejacket, you'll head straight for the bottom. Before cold shock was identified as the cause, this phenomenon was known as Sudden Disappearance Syndrome.
When news reports mention that a "Dive Team" is on scene, it's a clear sign that the victim wasn't wearing a lifejacket.
Witnesses say the victim went under and never resurfaced.
Hyperventilation
Gasping is immediately followed by hyperventilation - very rapid, out-of-control breathing. This can continue for a long time. In one near-death incident that we analyze in three parts, the victim was still hyperventilating 15 minutes after getting out of the water - and also suffering from hypocapnia, which is discussed below.
Swimming as short a distance as 6- 10 feet while hyperventilating is often impossible, even for good swimmers. When your breathing is out of control, swimming strokes cannot be synchronized with respiration. The result is swimming failure. If you're not wearing a PFD, you will drown.
Prolonged hyperventilation also results in hypocapnia, a medical condition which results from reducing the level of carbon dioxide in your blood.
Hypocapnia Can Cause
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Dizziness and feeling faint.
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Ringing or buzzing in ears.
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Numbness in fingers and toes.
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Hand and foot cramps.
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Mental confusion.
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Loss of consciousness.
Difficulty Holding Your Breath
Cold shock severely reduces the length of time that you can hold your breath. In water below 60F (15C) an average person can only hold their breath one-third as long as they can in warmer water.
The lower the water temperature, the greater the problem. One study of volunteers in 41F (5C) water found that average breath-hold time was reduced from 45 to 9.5 seconds, with one subject reduced to 0.2 seconds. It's easy to imagine how someone whose breath holding is reduced to a fraction of a second could gasp underwater and suddenly drown.
Flush Drowning
Loss of breathing control has ominous implications in rough water. It's likely a primary cause of cold water flush drownings - a whitewater term that refers to drownings that occur when the paddler capsizes and is repeatedly submerged while being washed downstream through rapids.
Submerged by waves.
Feeling of Suffocation
At the same time that they're hyperventilating, many people experience a strong claustrophobic feeling of not being able to get enough air. This frightening sensation, which continues for up to three minutes before gradually declining, increases the potential for panic and disorganized behavior in the water and makes it even more difficult for them to eventually gain control of their breathing.
Threat No. 2
Heart and Blood Pressure Problems
Cold water immersion causes an instantaneous and massive spike in heart rate and blood pressure which greatly increases the danger of heart failure and stroke in vulnerable individuals. This happens because sudden skin cooling causes all the blood vessels in your skin constrict.
The stress this places on your heart can also cause abnormal heart rhythms that could lead to sudden cardiac arrest. Research suggests that this can occur when a person is submerged in water temperatures below 60F (15C) while holding their breath. This has ominous implications for vulnerable individuals immersed in rough, cold water who hold their breath to avoid inhaling water.
Threat No. 3
Impaired Mental Ability
The moment you hit the water, cold shock causes a huge reduction in your ability to think and function. This can continue for a long time – even after you get out of the water. See A Closer Look, the 3rd article in our series about Randy Morgart's near-death experience on the freezing Mississippi River.
Mental Difficulties Include
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Disorientation
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Fear
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Panic
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Inability to think clearly
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Inability to evaluate options
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Inability to carry out a plan of action
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Freezing in place
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Failure to act
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Helplessness
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Lethargy
If the water temperature is below 45F (7C) add Severe Pain to the list
Real Life vs Physiology Lab Test
Cold shock is far more traumatic in real-life than in scientific research experiments. Learn More About It
Click To Start Video
If cold water is so dangerous, how can people do polar bear plunges without drowning? Watch this two minute video.