Cold Water Shock

Stephen Benton • May 1, 2018

What is it and what you should do.

Cold water shock is a condition which affects the body when entering cold water, this can happen even if you intentionally enter the water.

A large percentage of drowning in open water are actually caused by cold water shock.



What is cold water?


Anything below 15°C is defined as cold water and can seriously affect your breathing and movement, so the risk is significant most of the year.

Average UK and Ireland sea temperatures are just 12°C. Rivers such as the Thames are colder - even in the summer.


What happens?


When a person is immersed in cold water, the blood vessels in the skin close, this increases the resistance of blood flow and the heart rate is also increased.

As a result the heart has to work harder and your blood pressure goes up. Cold water shock can therefore cause heart attacks, even in the relatively young and healthy.


The sudden cooling of the skin by cold water also causes an involuntary gasp for breath. Breathing rates can increase as much as tenfold.

All these responses contribute to a feeling of panic, increasing the chance of inhaling water directly into the lungs.


An adult can start drowning if 1/2 pint of water enters the lungs.


These symptoms usually last around a minute.


What can you do?


  • Do not jump in to water, enter slowly
  • Wear a wet suit


If affected by Cold Water Shock


  • Try to stay calm
  • Relax and allow to body to float
  • Get out of the water before your muscles cool down
As your muscles cool, your strength, endurance and muscle control reduces to the point when you can’t swim any longer so can’t rescue yourself. The point at which you can’t swim any more is called ‘swim failure’, and if you haven’t got out of the water or managed to get hold of a buoyancy aid (like a lifejacket) by this time, you will drown.


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