Dos and Don'ts of swimming in cooler water
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The Cold Water Issue
It's May, late May, and water is beginning to cool for those of us in the Southern Hemisphere. If you take Donald Trump at his word, we are entering the most dangerous time of year for Covid-19, whilst those in the Northern Hemisphere are looking forward to the pandemic fizzling out, as if by magic, as summer approaches. Never mind. As it seems more and more punters are swimming all year 'round -- we have no data on this; it's just a gut feeling -- it's time for all of us to get smarter about swimming in cooler conditions, and to be more aware of the risks and how to handle them.
But rather than reinvent the wheel, we thought we should reprise two pieces that we ran over two years ago containing advice about how to handle cooler water. The first is by our fave anaesthetist, Snooze Doc Howard Roby, a swimmer in Sydney, who contributed this to us following the 2017 Bondi-Bronte swim, which was run in very cold (for Sydney) conditions. It struck us at the time that there is no body of knowledge available generally to swim awgies on how to manage their events in cooler water. The second piece comes from "The National Centre for Cold Water Safety", which is in the US, hence their copious use of Fahrenheit rather than Celsius. We have changed their use of "acclimation" to "acclimatisation". (We despise the North American abuse of English, but we recognise that we are witnessing the development of a dialect, and we must respect that.)
We reproduce these pieces in full, as they appeared at the time, Dr Roby's piece on April 21, 2018, and the US piece on March 14 the same year.
Here, too, is a guide to swimming in cold water by Charlie Evans, a swim coach and open water swimmer. It was drawn to all our attention by Bellywhackers, an "open water swimming collective" in Melbourne's Bayside area. You can follow Bellywhackers also on Twitter @belloywhackers... Click here
When is cold too cold?
Early this season, writes Howard Roby, controversy raged after the Bondi to Bronte swim was modified to allow swimmers to use wetsuits. This came about because of unseasonably cold water temperatures and the concerns of the officials about the possibility of some swimmers developing hypothermia. Snooze Doc Howard, an anaesthetist, offers this guide to dealing with hypothermia...
The term hypothermia refers to a core body temperature of below 35 degrees C, whereas normal core body temperature is around 37 degrees C.
Despite the change in the rules at Bondi-Bronte, some swimmers did need to be transported to hospital with hypothermia. I have seen different estimates of the water temp that day and have been told by the officials that the temperature during the swim was actually 13.7C. Due to the interest created by this swim, and as a committed ocean swimmer, I have been asked to write a piece on hypothermia. I am not an expert on hypothermia but I have qualifications in anaesthesia and intensive care where I spend a lot of my time and energy preventing patients from becoming hypothermic. I swam that race without a wetsuit and was very cold but I still felt as though I was functioning normally after it. I had a coffee an hour after the Bondi to Bronte swim with my friend, PJ, who is very fit but doesn’t have much fat. He was still slurring his speech and appeared drunk, although he kept telling me he felt normal.
First, some physiology
The human body functions well only within a narrow temperature range. A core temperature drop of 2 degrees C is dangerous and a 3 degreesC drop can kill you. Every cell in your body is a heat making machine. The act of burning energy creates heat. Even if you sit absolutely still, you are still using energy to keep your body functioning and thus producing some heat. The more exercise you perform, the more heat you produce.
Body temperature depends on a balance between heat production or gain and heat loss. In air, most heat is lost or gained by radiation as in warming from the sun. In water though, heat is lost mostly by conduction to the water. The colder the water, the more rapidly you lose heat and the faster your body temperature falls. In water below 34 C your body temperature will fall. The colder the water, the faster you’ll cool.
The major physiological defence mechanism you have to reduce heat loss is to constrict your surface blood vessels. This is why your skin is white when you’re cold and pink when you’re warm. In the cold, blood is shunted away from the skin and diverted towards your core. This increases blood flow to your kidneys which is one reason why you need to empty your bladder so often when you get cold. Shivering is an attempt by your body to increase heat production. It usually starts at a core temperature of around 34C but beware that it usually stops if your temp falls below 32C. Fat is an insulator, offering some protection against heat loss as well as increasing buoyancy.
Ocean swimmers are at particular risk of hypothermia because they are typically fit and muscled, with large surface veins. These carry blood just below the skin – which increases heat loss. Swimmers also typically have little fat to insulate them, also predisposing to rapid loss of body heat.
Swimming increases heat production in the muscles, but because it also increases blood flow to the muscles, and through the superficial veins, it increases the loss of heat through the skin. Moving the limbs through the water increases the flow of water across the skin, further increasing heat loss. The net effect is that swimming increases heat loss more than heat production; temperature falls faster when swimming than when floating still in the water.
Survival time in water depends on many factors, including water temperature. This makes estimating survival time difficult and often inaccurate. Published “survival tables” refer to specific conditions, but are hard to relate to different conditions of water and air temperature, wind strength, wave speed and height, presence or absence of clothing or wetsuit, flotation, head coverage or lack thereof, degree of physical activity, as well as physical factors such as muscle mass, natural insulation by body fat, natural buoyancy and proportion of the body on or above the surface – all of which affect rate of cooling.
SUDDEN IMMERSION in cold water causes marked and dangerous physiological responses. Most obvious is the gasp response: rapid, deep and uncontrollable breathing. Maximum breath hold time is reduced, and coordination between breathing and swimming action is lost. These contribute to a high risk of drowning within a very short period, even before getting to the first turning buoy.
Sudden cooling of the skin causes widespread constriction of the surface vessels, shunting blood to the body core. The sudden increase in blood flow back to the heart can cause a dramatic increase in blood pressure, and an irregular heart beat. There is an increase in production of adrenaline and noradrenaline, pushing the blood pressure and heart rate up even more.
Confusingly, sudden immersion in cold water can also cause the dive reflex, a sudden slowing of the heart, and a rush of cold water up the nose can exacerbate this or even cause the heart to stop. The competing effects of these contradictory drives can cause a dangerous, even lethal, irregular heart rhythm.
All of these responses occur when the body surface is first exposed to cold water; the core temperature has not yet changed at all - the person is not hypothermic.
For these reasons, cold water should be entered slowly. Before a cold swim, wade into the water, or allow water to enter your wetsuit just before you start the swim. This reduces the effects of sudden immersion in cold water.
Do the effects of sudden immersion decrease with repeated exposure? – a little, after a long period. Do not think you are immune!
From the sublime to the ridiculous. Well, not ridiculous, but from one extreme to the other: early morning swimmers from Armidale, on the NSW Northern Tablelands, enter Dumaresq Dam, where mornings a tad cooler than they are on the coast. Pic by Peter Hancock @platocean
Recognition of hypothermia
The initial response to cold water is constriction of the surface blood vessels, reducing heat loss via the skin. The initial feeling of cold on the skin lessens over a few minutes, as the temperature sensors in the skin become accustomed to the stimulus. As the tissues of the body lose heat, the body core temperature starts to fall. By 35oC there is reduced awareness of cold, often a feeling that everything is fine. Muscle strength is reduced. Muscular activity is less efficient, swimming less coordinated and less powerful. There is reduced ability to recognise the deterioration in function. Speech is slurred, reflecting impaired brain function – people like this have been mistakenly assumed to be drunk. Between 34 and 35oC mental acuity is markedly impaired. Judgement and memory are impaired, and with it the ability to remember training, to recognise danger, and to act logically. Swimmers are likely to miss buoys, change direction the wrong way, fail to avoid waves or swell, and are unlikely to signal for assistance. At this stage they may be seen to be swimming, but not making any headway.
Mentally there is a determination to keep swimming, without any understanding of what is happening. There is no awareness of the need for immediate rescue. By 34oC thinking, reason, memory and awareness are very limited. Extreme lethargy gives way to a desire to sleep; this precedes a decrease in conscious level, predisposing to a quiet, un-noticed disappearance below the water and drowning.
Because the hypothermic swimmer does not recognise that they are becoming hypothermic, control of the swimmers must be exercised by people who are not in the water. (Tasmania Police Rescue divers in water of 12 - 13C, wearing two layers of thick wetsuit with hood and boots, are under the control of a diver in the mother boat for this reason.)
What water temperature is safe for swimming?
To a small degree this depends on acclimatisation. People in Canada and Europe tolerate lower water temperatures than we do, but usually for shorter swims. They often have higher body fat content, and may use artificial insulation.
The physiological effects are dramatically increased in water below 15oC so this might be a reasonable absolute minimum. Between 15 and 20oC an acceptable water temperature would depend on the wind, waves, wetsuits and head covering, sunshine, individual physical makeup, the length of the swim, and the other variables mentioned earlier.
Does gender make a difference? Females have a slightly higher total body fat percentage, so a little more insulation, and have a higher surface area to mass ratio. Males typically have a higher muscle mass, so producing more heat. The net effect is probably a small difference between male and female ocean swimmers, with females at slightly more risk.
Prevention of hypothermia
Make assessment of water and weather conditions a formal part of every swim GO or Postpone decision. Ensure you have a club doctor who is well informed on hypothermia, is part of the decision-making process, and listen to his or her advice.
In cold conditions, keep as warm as possible before starting the swim. The warmer you are before you start, the longer it takes to become cold. DO NOT walk around uncovered, thinking you are getting yourself ready / used to the cold.
Make sure you are well hydrated.
- In cold water, below about 20C, always wear at least one swim cap. In lower temperatures, wear two.
- When to wear a wetsuit depends on water temperature, degree of warmth from the sun, wind strength, wave height and velocity, and how far the swim is, as well as your physical characteristics. Some examples -
- a swim of 1.5 km in water 0f 17C, without a wetsuit, is likely to leave a swimmer mildly hypothermic, looking pale, shivering, and feeling cold;
- a swim of 5 km in water of 20C, by a swimmer with a little body fat, no wetsuit, is likely to leave him or her mildly hypothermic, looking pale, shivering, and feeling cold;
- the same 5 km swim, but in water of 21C, by a thin muscular swimmer with large surface veins, without wetsuit, is likely to leave the swimmer very cold, visibly affected and under-performing;
- an 8 km swim in water of 20C, without wetsuit, is likely to cause moderate, and dangerous hypothermia in many of the swimmers;
- a 10 km swim in water under 20oC is likely to leave most swimmers moderately hypothermic, and some in hospital.
So, there are no good rules, but it would seem sensible to consider wearing a wetsuit in any swim under 17C, or any swim over 5 km.
Ocean swimming is meant to fun, not a trial of survival!
Forster, last week.
Management of hypothermic swimmers
- Recognise that their performance is impaired;
- Understand that they may not realise this, and argue with you;
- Get them out of the water;
- Shelter them from wind;
- Dry them, cover the whole body in dry clothing / blankets, particularly the head. If they are conscious, keep them wrapped up, and allow them to warm themselves by their own heat production. They must be carefully observed, as their core temperature may continue to drop and they may lose consciousness;
- Give them warm, not hot, sweet drinks. Warmed blankets are useful, as is body-to-body contact;
- The ubiquitous space blanket that looks like a giant piece of aluminium foil may not be all that good for treating hypothermia. If you’re warm, they are good at keeping you warm. They won’t rapidly warm up someone who is cold;
- Active heating with a specially designed forced air warming blanket is preferable to a space blanket;
- DO NOT leave them alone;
- DO NOT use hot water bottles or chemical heating packs, as these are likely to result in burns;
- DO NOT put them in a hot shower or bath; rapid warming causes the superficial vessels to dilate rapidly; blood pressure falls dangerously, cold blood trapped in the periphery is suddenly released, and a bolus of cold blood returning to the heart can cause a fatal irregular heart beat.
Once they are rewarmed, their swim for the day is over. Do not allow them to re-enter the water.
Unconscious or semi-conscious people should be treated as above, on their side in the coma position with airway support, and transported by ambulance to hospital for more intensive management.
Should Bondi-Bronte have been cancelled?
I’m not smart enough to know the answer to that but I hope the organisers understood the dangers. Swimmers may rapidly get hypothermic and have breathing and heart difficulties before they even get to the first buoy (as happened to one of my colleagues) or they may start to act irrationally midway through the swim. They may turn out to sea and start swimming away from then land or they may drown.
In summary, if you are thinking of swimming in cold water -
- Consider how long you’ll be in the water for;
- Consider the weather conditions;
- Wear at least one bathing cap;
- Consider wearing a wetsuit;
- Keep yourself warm leading up to the swim but make sure you’ve entered the water slowly when you do get in;
- Make sure someone who is not in the water is keeping an eye on you.
Howard Roby is an anaesthetist at St Vincents Hospital in Sydney, a former water poloist, and a regular ocean swimmer. Dr Roby has two Cole Classic plates.
We all have our own styles.
What is cold water?
Cold water can kill you in less than a minute. It's actually so dangerous that it kills a lot of people within seconds. Thousands of people have drowned after falling into cold water and a lot of them died before they even had a chance to reach the surface.
That's a scientific and medical fact that most people have trouble understanding - because they have no personal experience actually being in cold water. When they hear or think about 50F (10C) water, it doesn't sound particularly cold - or dangerous - because they're mentally comparing it to 50F (10C) air. It's a big mistake that gets a lot of people killed each year. This is explained in much greater detail in the section Why Cold Water is Dangerous.
You should treat any water temperature below 70F (21C) with caution.
Water Temperature Safety Guide
Below 77F (25C)
Breathing begins to be affected.
This is why the official water temperature required for Olympic swimming competition is 77-82F (25-28C).
70-60F (21-15C) Dangerous
Controlling your breathing and holding your breath becomes progressively more difficult as water temperature falls as water temperature falls from 70°F to 60°F (21°C to 15°C).
True or False: You don't need thermal protection when the water temperature is above 60F (15C). False. You should certainly be wearing a wetsuit or drysuit below 60F, however, 60F (15C) is not the temperature at which most people should start wearing thermal protection.
60-50F (15-10C) Very Dangerous/Immediately Life-threatening
Total loss of breathing control. Maximum intensity cold shock. Unable to control gasping and hyperventilation.
Fact: Cold shock is as extreme between 50-60F (10-15C) as it is at 35F (2C).
Most people who are unaccustomed to cold water will experience a maximum cold shock response somewhere between 50-60F (10-15C). For some individuals, this happens at 57F (14C), for others, the peak occurs at 52F (11C) and so on.
This means that an unprotected immersion in this temperature range will cause most people to completely lose control of their breathing – they will be gasping and hyperventilating as hard and fast as they can.
Since cold shock reaches its maximum intensity between 50-60F (10-15C), it can’t get any more intense at lower water temperatures. In other words, breathing control, once completely lost, cannot be lost to a greater degree.
Below 40F (5C) Very Dangerous/Immediately Life-threatening
Total loss of breathing control. Unable to control gasping and hyperventilation. Water feels painfully cold.
Below 40F (4.5C), water is so painfully cold that it often feels like it’s burning your skin. For many people, the notorious “ice cream headache” can be triggered simply by water touching your face. Even though cold shock is no more intense than it was between 50-60F (10-15C), the severe pain makes a desperate situation even worse because it greatly increases your psychological stress. Clear thinking becomes almost impossible.
Ken cops it: Ken Maytom, in just the right spot to absorb the dump. Forster.
See for Yourself
If you're in good physical shape and feeling adventurous, a very memorable way to find out about cold water is by conducting a personal experiment. First, make sure the tap water is as cold as it will get by running the faucet for a minute or two, then fill a glass and measure the temperature.
When you're feeling brave, get in the shower and turn it on full blast. No shower? No problem. Have a friend spray you with cold water from a garden hose while you're wearing a bathing suit.
Warning:Don't try this unless you're completely healthy because the shock of cold water hitting your skin will cause an immediate, and often dramatic, increase in your blood pressure and heart rate. If there's any doubt in your mind, check with your doctor
- 98.6F(37C) Normal body temperature measured with an oral thermometer.
- 99.6F(37.5C) Deep body or core temperature measured with a rectal thermometer.
- 95F(35C) For medical purposes, this is the clinical point at whichh hypothermia begins.
- 91F(32.7C) The temperature of your skin.
- 85F(29.4C) Water feels pleasantly cool rather than warm.
- 77-82F(25-28C) Swimming pool temperature range for Olympic competition.
- 70F(21C) Water feels quite cold to most people. Treat any water temperature below 70F (21C) with caution.
- 40F(4.4C) or lower Water is painfully cold.
Not strictly ocean swimming, but a glorious autumn image from Avalon, on Sydney's Northern Beaches, by (Sydney Morning Herald and freelance) photographer Dallas Kilponen, himself a swimmer and a surfer from Sydney's Eastern Suburbs @dallaskilponen
Most people unfamiliar with cold water find 70F (21C) to be quite cold. On the other hand, a competitive open-water swimmer who is used to swimming in 55F (13C) water will probably think that 70F (21C) doesn’t feel very cold at all. What’s important to your safety is how you personally respond to cold water.
Acclimatisation and body fat can make a significant difference in how someone responds to cold water.
Acclimatisation is a process by which your body gradually adapts itself to cold water through repeated exposure. Through acclimation, it’s possible to improve circulation to the hands during cold water immersion, and to greatly reduce or eliminate cold shock.
Body fat is an excellent insulator. Seals, whales, and other warm-blooded aquatic mammals have a lot of this insulating fat - called blubber - which enables them to keep warm while swimming in cold oceans.
Because fat provides insulation from the cold, it can delay incapacitation and hypothermia and also improve physical stamina in the water. Repeated exposure to even cool water increases the layer of fat directly under the skin surface (subcutaneous fat).
You can easily see this body fat difference by comparing the physical appearance of Olympic swimmers and runners. Swimmers have a lot of subcutaneous fat and a sleek, streamlined look. Runners have very little fat and more obvious muscle definition.
Acclimatisation reduces the intensity of cold shock
Acclimatisation does not protect you against incapacitation, swimming failure and hypothermia.
Body fat does not reduce the intensity of cold shock.
Body fat provides insulation, slows heat loss, and delays incapacitation and hypothermia.
A Very Remarkable Swim
An excellent example of how body fat can prolong cold water survival is the remarkable case of Icelandic fisherman Gudlaugur Fridthorsson. On a cold night in March, 1984, Fridthorsson was working on a 75 foot (23m) commercial fishing vessel when the nets snagged on the ocean bottom and she capsized three miles off the rugged coast of Heimaey Island.
Although he wasn't a particularly good swimmer, Fridthorsson swam for six hours in 41-43F (5-6C) water before reaching shore. He was the sole survivor of the five-man crew. How in the world did he do it? In a word, he was obese. At 6'4" and 125kgs, he had a chart-busting BMI in excess of 30. His physique was similar to a seal’s.
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New Swipes in stock now
We've been deluged with orders for the new View Swipe gogs. View is moving most of its goggle styles to Swipes, but we have so far just two models available -- the Selenes, which were our most popular gog even before the Selene Swipes were released late last year, and now also the Wide-Eyes. Both come in both regular and fully-sick mirrored versions, each in various groovy colours. The Wide-Eyes cater to swimmers who prefer an adjustable nose bridge, and a slightly wider field of vision than offered by the Swipe Selenes. They will be more suitable, perhaps, for punters who need a longer or narrower nose-bridge.
We wore our original View Selene Swipes for 56 outings, until we lost them at Bondi. Left them in a change room. Now, we're using the new Wide-Eyes Swipes.
We had been cautious about promoting the Swipes when we heard about them from the folk at View. We wore them 30 times before we were comfortable with flogging them to you. If they do fog at all, generally it's in one corner of a lens. Each time, we took them off, wiped the foggy bit gently with our forefinger, and no more fogging for the rest of the session. No goo, no spit, no nothing, except wetting them and wiping them carefully. Be careful, all gogs will fog if they're not looked after, and all gogs will collect scum from the water in which they are used. They must be kept clean. They must be respected.
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According to the makers, the "10 times as long" refers to distance they say you can swim before you start to see some fogging with new goggles. They say the standard is 4km, but the Swipes will go 40kms. Whatever, all gogs will fog if you don't respect them and look after them. The issue also is how to deal with the fogging if and when it does occur.
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fos tallies 19/20
Preliminary tallies for inspection, critique
We also reproduce here our story from our last newsletter on our fine ocean swimmers' tallies for the season just ended. We have received some representations from swimmers who pointed out some errors in the original draft tallies, and we publish them again to flush out more. We're reluctant to publish "final" tallies until we are confident that pretty much all errors have been identified.
Why are there errors? Largely because of the incomplete nature of many events' results, and the consequent difficulty in distinguishing amongst some swimmers. But read on, you'll understand why...
It’s a bit earlier than usual, but we have posted our preliminary fine ocean swimmers’ tallies for the truncated season 2019/20. The tallies total the swims and distances for each and every ocean swimmer, in a formal ocean or open water swim in Australia or New Zealand, or in an array of overseas swims in which swimmers may participate, in season 2019/20.
Season 2019/20 was cut short by the Covid-19 pandemic, so tallies are lower than they would be in a normal, full-length season. Our seasons run from June 1 through May 31.
Note that the tallies are preliminary. We advise you to check the lists to ensure that all your swims are recorded. If there are errors, there are links on the page on oceanswims.com to contact us to let us know. We will amend appropriately.
Understand that many organisers, and many timers, are sloppy with their reporting of results. They record only name, usually — but not always -- gender, sometimes age, but only rarely other identifying data, such as where a swimmer is from. Often, too, their input of data is misspelt or otherwise in error. This means that it is often very difficult to identify swimmers, and to separate swimmers with similar names. Thus, some swimmers will appear several times in these lists as if they are different swimmers. We need you to check the lists and to draw these anomalies to our attention, so that we can then edit the master list to ensure the final tallies are as accurate as we can possibly get them.
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