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 are very likely to drown. Even with the added buoyancy of a PFD, your mouth is very close to the surface of the water.
When your muscles and nerves get cold enough, they simply stop working. This loss of 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 cold water cools your muscles and nerves:
Swimming failure at Stage 1 (Cold Shock) results from loss of breathing control, but here in Stage 2 (Incapacitation), it’s the result of muscle fatigue, loss of sensation, and loss of motor control, particularly in your arms and hands.
When your hands get too cold, the fingers also stiffen and become splayed (spread apart) which further compromises swimming ability.
Dealing with Waves
The safest position in the water is with your back facing the waves because 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 up and into your face, making it far more likely that you will inhale water and drown.
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.
Rough Water Test
BoatUS tested recreational (Type III) PFDs 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”. When simulating an unconscious victim, the testers “repeatedly sank well beneath the surface as the waves rolled over them”.