State Parks Utah
Physical incapacitation is another way of saying that you’ve become physically helpless in the water because you can no longer control your arms, legs, hands and feet. 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.
When your muscles and nerves get cold enough, they simply stop working. 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.
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. It's possible to lose the use of your hands in minutes in very cold water.
When Cold Water Cools Your Muscles and Nerves
You become progressively weaker.
You become exhausted more rapidly.
Your hands become numb and useless.
Your arms and legs stop working.
What This Means
Unable to grab and hold anything.
Unable to use a phone or VHF radio.
Unable to self-rescue.
Unable to assist other people who try to help you.
Unable to position your back to the waves.
Greatly increased risk of drowning.
Dealing With Waves
When you're floating in rough water, 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. In that position, your PFD also tends to direct wave splash into your face, making it far more likely that you will inhale water and drown.
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.
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. Survival charts are notoriously unreliable because they fail to account for either of these problems.
Rough Water Test
BoatUS tested recreational PFDs (Lifejackets) in rough water with seas up to 4 feet. They reported that experienced lifeguards “had to work hard treading water to keep their faces clear of the waves”.
But their most ominous finding happened when the lifeguards simulated an unconscious victim. They reported that the testers “repeatedly sank well beneath the surface as the waves rolled over them”. This is precisely what happens when someone becomes incapacitated by cold water.
We examine this issue in greater detail in our Special Report - What PFDs Can and Can't Do.