Physical Incapacitation
State Parks Utah
Hanging helpless in the water.
When your muscles and nerves get cold enough, they simply stop working. Physical incapacitation is another way of saying that you’ve become physically helpless because you can no longer control your arms, legs, hands and feet. This loss of sensation, muscle strength and control can happen very quickly. In very cold water, it’s possible to lose the use of your hands in under a minute.
When this happens, particularly in waves, you're very likely to drown. Even with the added buoyancy of a PFD, your mouth is very close to the surface of the water.
See Dealing With Waves below.
Children, with their smaller body size, cool faster than adults. On the other hand, a very large person with a lot of body fat can delay both physical incapacitation and hypothermia, sometimes for hours.
Swimming Failure
With Cold Shock, swimming failure results from loss of breathing control, but with Incapacitation, it’s the result of muscle fatigue, loss of sensation, and loss of motor control, particularly in your arms, legs, hands and feet. The colder the water, the faster incapacitation occurs.
Also, when your hands get too cold, your fingers stiffen and splay (spread apart) which further compromises swimming ability.
When Your Muscles and Nerves Become Chilled
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You become progressively weaker.
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You become exhausted more rapidly.
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Your hands become numb and useless.
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Your arms and legs stop working.
What This Means
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Unable to grab and hold anything.
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Unable to use a phone or VHF radio.
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Unable to self-rescue.
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Unable to assist other people who try to help you.
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Swimming failure.
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Unable to position your back to the waves.
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Greatly increased risk of drowning.
When you're floating in rough, open water - like the ocean or a lake - the safest position is with your back facing the waves. Breathing is easier, and holding your breath is automatic when a wave hits you from behind.
However, keeping your back to the waves is impossible when you’re incapacitated, because wave energy will naturally rotate your body until you’re facing the waves head-on and you won't have the physical ability to counteract that rotation. When facing the waves, your PFD (lifejacket) also tends to direct wave splash into your face, making it far more likely that you will inhale water and drown.
Dealing With Waves
Mouth-To-Water Distance
When you're wearing a standard USCG Type 3 PFD (lifejacket) - the kind worn by most recreational paddlers - the average distance from the water surface to your mouth in flat-calm water is 3 inches. This is why inhaling water is such a threat when conditions are rough, and is the likely cause of whitewater flush drownings.
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Gradual Drowning
Cold water drowning can happen immediately, but it can also take a fairly long time – a gruesome process in which small amounts of water are inhaled, over and over again, until your lungs become so waterlogged that you suffocate.
Floating Face Down
Holding your head up and keeping your face out of the water also requires effort, and recreational PFDs are not designed to prevent you from floating face-down if you become helpless or unconscious.
See: What PFDs Can and Can't Do
Surviving Cold Water Immersion
Survival charts are notoriously unreliable because they fail to consider drowning due to cold shock and incapacitation.
Rough Water Test
BoatUS tested recreational PFDs (Lifejackets) in rough water with seas up to 4 feet. Their report pointed out that experienced lifeguards “had to work hard treading water to keep their faces clear of the waves”.
Their most ominous discovery happened when the lifeguards simulated an incapacitated or unconscious victim. They reported that the testers “repeatedly sank well beneath the surface as the waves rolled over them”.