Cold Water Shock
An RNLI Message on Cold Water Shock and Lifejackets
Cold Water Shock
“It’s Ok, I’m a strong swimmer” – a phrase that more than one of my students has uttered to me in response to being told to wear a lifejacket.
When I’m teaching any level of sea-based practical training the first and usually only ‘rule’ that I fully insist on is the wearing of a lifejacket when we are underway (and even when we are preparing to get underway). Why? Well, I have the advantage of experience and knowledge. Many years ago I was on a sailing boat where we lost someone overboard who wasn’t wearing a lifejacket. It was only luck that allowed us to get them back alive… but that’s another story. My own training is sea survival has made it very clear what the risks are and how you can go about minimising those.
Another term used is PFD or Personal Flotation Device.
What is Cold Water Shock?
The RYA publishes an excellent book by Keith Colwell called the ‘Sea Survival Handbook’. In the book is a section dedicated to survival in cold water. Put simply, cold water shock is the reaction from your body that occurs between 30 seconds to three minutes in response to being immersed in cold water. And, if you are wondering what the definition of ‘cold water’ is – anything below 15C.
Considering the UK’s sea temperatures annually range from 5C to 18C with an average of 12C we should be aware of the dangers.
You are going to experience hyperventilation – an increase from a breathing rate of about 10 breathes per minute to around 60 per minute.
Your ability to hold your breath (might be useful in the sea…) will be reduced from times of over a minute to less than 10 seconds.
You will probably start to ingest sea water due to involuntarily gasping – something you can’t stop even if you find yourself underwater.
Your blood pressure will increase significantly as blood vessels near the skin react to the cold water and shut down. Depending on how fit you are, this may be the trigger of a stroke or heart attack.
The facts are that you are more likely to drown from entering cold water quicker than you are from hypothermia.
The RNLI are a great source for videos that bring the message into reality. Although this is aimed at the fishing industry it is equally relevant to sailors. Watch this video:
What can you do?
Well, hopefully now you will understand why I insist on all my crew/students wearing a lifejacket. Interestingly, research shows that if you get into the habit of taking cold showers (or baths/sea swimming) you can ‘condition’ your body to cold water shock. Tests indicate that after a week of daily cold showers the effects of cold water shock may be reduced by 50%.
Additionally, get fit – the better shape you are in, the more chance your body has to withstand cold water shock.