By SUSAN DAY
with permission from Jane Blockley to summarise her excellent 2005 article
A tale from the ex-Vice President of NSW Sea Kayak Club
“It was a lovely summer day on the Tully in North Queensland. We had been rafting, but for the next rapid, we were going to ‘bum’ it down to where the tour guide would wait for us in the raft. The guide instructed us all to sit with feet facing downstream with legs around the hips of the person in front and to hold onto their lifejacket. There were 6 of us. I was at the end of the train of people. The river carried us through a 2m wide slot over a 1.7m drop. We landed in foaming deep water on the other side. When I came up for air I found I couldn’t breathe in or out, I couldn’t cough, I couldn’t speak. The bank was only 3m away. Nothing like this had ever happened before. I know from my diving experience that CPR on the water is pretty hard so I realised I had to get onto the bank before I passed out and hopefully someone would see me there and realise that I was not responding. I did several strokes of breaststroke and was half way to the bank when all of a sudden I was able to take in a huge gasp of air. So I turned around and breast stroked back to the raft where the others were. I now know that this was a brief experience of the reflex closing of the airway that causes silent ‘dry drowning’.”
I am a swimming teacher and part of the training includes understanding the effects of cold water on learning and on survival. Knowing the hazards of cold water and being prepared to deal with them is relevant to kayakers, particularly when we roam to colder coastal waters or venture to inland waters (although for small skinny people, some things are relevant in NSW coastal waters).
Please refer to the three references listed below. The almost exclusive source of this summary is Jane Blockley’s ‘Cold Water – How to increase your chance of survival’. I have paraphrased her article and amended it in a minor way to relate it more to kayaking.
If water is below 26.5°C it will have an adverse effect on survival (Blockley, 2005):
“Predicted survival curves”, which give an expected survival time when immersed in water at various temperatures are of limited use. They are based on rates of body core cooling. However, the early localised effects of hypothermia may be fatal long before body core temperature reaches life-threatening levels. For example, manual dexterity is rapidly and severely degraded in water below 15°C, badly hampering the ability to carry out essential survival tasks.
The hazards of cold water may apply to you whether you are fully immersed or if you have just had to roll unexpectedly and intend to continue paddling along in strong winds.
What is cold water?
What is ‘cold’ is not just about the temperature of the water but also sea state, wind, the individual and factors which affect heat loss. The rate of heat loss is dependent on several factors, including
Difference between the temperature of your body and the water
Body size and amount of insulation from clothing and body fat
Factors increasing heat loss such as movement of cold water against the body due to sea state or physical activity which draws warm blood from the core to the limbs.
Wearing a life jacket (which insulates and reduces the need to tread water or swim)
Lack of protection of parts of the body which lose heat faster than others i.e. the head (50% of heat loss), neck, armpits, chest and groin
Fitness, hydration and energy levels (diet prior to immersion)
According to AMSA 2010, if water is above 21°C, survival depends on fatigue not water temperature; in 15-21°C people can survive up to 12 hours; in 10-15°C up to 6 hours. Port Phillip water temperature varies from 9.5°C to 23°C. Sydney coastal water average temperatures vary from approximately 16°C to 25°C; greater variation is possible after heavy rain, close to rivers or if strong offshore winds or currents cause colder deep water upwelling.
Recent anecdotal evidence suggests that the water at Northbridge baths dropped to 11°C after a week of very heavy rain during July and can increase up to 27°C in summer. It is 14-16°C in August. These temperatures are sufficient to make the 5 hazards, listed below, relevant to local kayakers.
What cold water does to YOU
Cold water affects:
Your ability to think clearly – this affects your judgement, ability to make decisions, speed of reaction, concentration and awareness of surroundings.
What you can do physically and how well you can do it: it affects your ability to hold your breath, your manual dexterity and coordination; it reduces grip strength and causes limb numbness, stiffness and pain.
In addition, physical activity in cold water, such as re-entering your boat or swimming, hastens hypothermia and reduces survival time. Treading water or swimming increases the rate of heat loss by approx 40%.
The 5 ways YOU could die in cold water
1. Dry drowning
When: can occur the instant you enter the water or any time after; it may occur in up to 20% of drownings.
What: It is caused by the automatic reflex closing of the airway due to muscle spasm in response to the shock of cold water hitting the back of the nose or throat. As a result, no water can enter the lungs, but neither can air.
Action: Avoid getting water or spray into your nose or throat. If possible take a deep breath, pinch your nose with your fingers to close the nostrils, keep your mouth closed and enter the water gently by rolling in, rather than feet first.
2. Cold shock
When: occurs below 25°C and peaks between 10-15°C; max risk at 1- 5 minutes; lasts for approximately 1 – 3 minutes.
What: At first there is an involuntary in-drawing of breath which is followed by rapid and disordered breathing. There is usually also some disorientation.
Action: If the first involuntary gasp takes place when your face in is the water, then you will get a lungful of water instead of air. If you are in choppy water and your breathing is uncontrolled and you are feeling disorientated then you may have difficulty co-ordinating breathing with gaps between the waves. In order to NOT drown you must concentrate on keeping your face out of the water: turn your back to the waves to avoid inhaling spray and water and try your hardest to control your breathing. Remind yourself it will soon pass.
3. Swimming failure
When: risk increases with time in the water. The colder the water the more your swimming deteriorates. This effect takes hold long before there is significant cooling of the body core, so is not due to core hypothermia. These effects are thought to be due to local cooling of the limb muscles.
What: It becomes more and more difficult to straighten the limbs and to co-ordinate swimming movements. The fingers splay and start to flex. As a result, stroke length is decreased, stroke rate is increased and body position becomes more vertical – so the stroke becomes less and less efficient, and more exhausting. Wearing a PFD does not prevent the onset of swimming failure.
Action: avoid swimming in cold water as much as you can – rescue by swimming should be a last resort only. Different people are affected by swimming failure to varying degrees. Some are affected very rapidly, and others are able to swim for reasonable distances before the effects take hold. In one experiment the significant factor seemed to be upper arm skinfold thickness. The more insulation around the muscles, the warmer and more efficient they remain. According to the Recreational Boating reference below, at a water temperature of 10°C, about 0.85 miles (1.36km) would be the greatest distance that a person of average build is likely to swim before being overcome by hypothermia
When: max cause of death at 30 minutes plus. However long it takes your body core temperature to drop more than 2°C (from 37°C to below 35°C). Predicted survival time for a fully clothed adult male wearing a lifejacket in water at 5°C is approx 1 hour, and 2 hours at 10°C. A thin small person would not last as long. Hypothermia can kill even after the victim has been rescued from the water.
What: As core temperature drops, brain and physical function is impaired. The heart rhythm, cough reflex and blood thickness may be affected. Increased urine production can cause dehydration.
Action: get out of the water as much as possible but avoid unnecessary movement and protect against heat loss then decide what to do given timing of possible rescue by others, the proximity of dry land and how easy it would be to get out of the water, whether you can paddle or not, and whether there are any hazards nearby.
5. Post rescue collapse/‘after drop’
When: risk on or shortly after rescue.
What: there could be circulatory collapse or heart failure. Inappropriate warming may result in cold blood from the extremities entering the core or warm blood being drawn away from the core, resulting in a further drop in core temperature, which may prove fatal.
Action: keep horizontal and still to avoid circulatory collapse or heart failure. Apply insulating blankets and create a warm environment. Go to hospital
How to survive
Do not put yourself at greater risk by paddling if ill, fatigued, dehydrated, hungry or affected by alcohol/drugs
Avoid immersion in cold water no matter how good your roll is – dry drowning or cold shock may mean you don’t roll up
Know how well your body copes in cold water and be aware of warning signs
Factor the hazards into your risk assessment – given that kayakers are often distant from shore and in remote locations and swimming is not a good option
Understand the 5 hazards so you can work out the best course of action for you if you end up in cold water
Wear a PFD and layers and cover your head which accounts for 50% of body heat loss. Wear bright colours for rescue
2. After immersion
Try to control position of entry to avoid water getting into your nose and throat. Try to control breathing if affected by cold shock. Keep your back to the waves and avoid water inhalation
Stay in/on your boat to keep as much of your body core out of the water as possible. If you can’t, stay as still as possible in the water and protect high heat loss areas by tucking in a ball or huddling in a group. Refer to the HUDDLE position and Heat Exchange Lessening Posture (HELP) to conserve body heat. If you are compelled to tread water or swim to stay afloat due to lack of PFD or sea state, you reduce survival time by 50%.
Think through your options in terms of the hazards and your physical state. Swim as a last resort. When out of the water, if affected by cold, lie down for at least 30 minutes, wrap up and get to hospital.
Notes from personal experience
I always wondered why so many people drown so close to shore – the 5 hazards could explain some of the deaths. Ken has experienced reflex closing of the airway (not long enough to drown, but long enough to wonder why on earth he couldn’t breathe) when rafting in Nth Queensland in the Tully River. I have experienced mild forms of swimming failure in a triathlon in a lake in Canberra in mid-summer and in a billabong near Ayers Rock. I realised it was hard to make my arms go around and that it was because it was cold, so I just tried to swim harder to generate more heat. I didn’t realise I was both generating more heat and losing it more efficiently. Next time I might just head back to shore or test the waters a bit more carefully before I launch myself in.
Jane Blockley, 2005, ‘Cold Water – How to increase your chance of survival’ http://www.rowingtas.asn.au/uploads/safety_docs/cold-water-survival.pdf : For young rowers – lists different hazards of cold water & how to prepare for them
Recreational Boating in the State of Victoria, date unknown. ‘Immersion Hypothermia ‘http://member.melbpc.org.au/~trinc/hypotherm.html : Good easy reading article for Melbourne water temperatures; shows HUDDLE & HELP positions
AMSA, 2010. ‘National Land Search Operations Manual’, http://natsar.amsa.gov.au/Manuals/Land_Search_Operations_Manual/documents/LSOM_Chapter_9.pdf (More technical but relevant to water temperatures near Sydney)