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education & Training
education & Training
Feature
Surviving
the Big Chill
Understanding cold
water immersion
Peter Hopkins,
Marine and Safety Tasmania
“Hypothermia may not be the major cause
of death in cold water immersion situations.
Studies show that up to 60% of cold water
immersion fatalities occur in the first 15
minutes, before the body core temperature
cools to hypothermic levels.”
Most of you will have dived into water so cold
that the chill has literally taken your breath away.
Or, you may have even unexpectedly fallen
overboard into cold water after losing your footing or
missing a handhold when forgetting the golden rule,
“one hand for the boat and one hand for you”! Ending
up in cold water can be very dangerous, especially
when it is unexpected.
In many parts of Australia, particularly in southern states, the
average water temperature in summer can be around 19°C off the
coast. However, in winter the water temperature can drop to as low
as 15°C, and the further south you go the lower it can get (10°C or
below). Inland and alpine waters also get extremely cold and
temperatures can be as low as 2°C.
Studies have shown that cold water carries heat away from the body
25 times faster than air at the same temperature. Because of this,
the body core begins to lose heat to the outside environment and
we begin to shiver in an attempt to generate more heat. However,
shivering will not be enough to offset the loss of heat to the water,
and depending on the water temperature, judgment can become
affected within 20 or 30 minutes as the core body temperature
drops below 35°C.
The table shows how your body may behave in cold water and the
average expected survival time. However, it must be remembered
that everyone’s response to cold water will vary depending on the
amount of body fat, activity in the water, and clothing worn.
You don’t have long in cold water before experiencing a lack of
coordination and dexterity if you’re not wearing protective clothing.
Many of us have been in a situation where we have been so cold
that it’s been difficult to undo a shackle, tie a bowline or get a zipper
done up on wet weather gear—but being in water is far worse.
1-10-1
At the Marine 15 Conference on the Gold Coast in May 2015,
Dr Gordon Giesbrecht spoke on cold water shock immersion,
explaining the 1-10-1 (1 minute—10 minute—1 hour) concept for
managing immersion in water temperatures less than 15°C. The
times are approximate, but the essential strategy remains the same.
Dr Giesbrecht considers that once you’re in the water you will
hyperventilate for one minute. During this time you will need to
control your breathing and keep your mouth clear of the water. In the
first minute, you must try not to panic and plan your next steps.
Water loss of dexterity Exhaustion or Expected
Temperature °C with no protective unconsciousness survival time
clothing
0.3–4.5