Cold Water Shock

Cold Water Shock is a real danger in water below 15°C . If you do find yourself in the water a life jacket could literally save your life.

Immersion in cold water rapidly incapacitates you and can kill you.

The sudden exposure of your head and body to cold water can cause a number of involuntary body reactions – this condition is known as cold water shock. It is one of the most profound stimuli that the body can encounter and it cannot be prevented. It can be as swift as it is deadly.

Because cold water shock occurs well before the effects of hypothermia, it is far deadlier, yet less understood, by the recreational boater.

Hypothermia kills over a period of time, as heat is conducted away from the body leading to a gradual decline in body core temperature, the loss of swimming ability, unconsciousness and ultimately death.

In contrast cold water shock can be lethal in minutes as it can cause a number of instant, powerful, involuntary respiratory reflexes, such as sudden increase in heart and blood pressure that may result in cardiac arrest, even for people in good health. Your ability to ‘swim like a fish’ will have no impact on your body’s involuntary response.

At a water temperature of below 15°C, and if you are not wearing a life jacket, especially an automatic one, cold water shock will:

  • cause you to inhale as you go under the water, due to an involuntary gasping reflex, and drown without coming back to the surface 
  • drastically reduce your ability to hold your breath underwater, typically from a minute or so to less than 10 seconds
  • induce vertigo as your ears are exposed to cold water, resulting in failure to differentiate between up and down.

Think about the temperature of the water, make sure you are wearing a lifejacket, unless you have assessed it is safe not to do so and clip on your safety line when the situation and weather dictate it.

Related page

Buoyancy Aids and Lifejackets