One big ice cube – swimming in cold water

Many of us ‘retire’ from open water swimming for the winter.  Some of us have the excuse that our dear little puddle of water is frozen over.  And then there are those of us that simply turn off the thought of open water swimming until both the air and water temperatures warm up.

A recent post by “The Science of Sport” discusses some of the science behind cold water swimming.  In addition, a recent document discussing cold water swimming from USMS – included swimming at the North Pole.

What the Science of Sport folks say is that basically as long as you keep moving – you’ll be fine.  Now, do caveat that with the usual always swim with a buddy, etc… – but by and large if you keep moving and keep it to about 30 minutes you’re in the safe zone.  Here’s a little snippet from their site:

“Perhaps the first, and maybe the most surprising fact about cold water physiology, is that your body has too much heat to become hypothermic within about 30 minutes, no matter how cold the water is! In other words, it is not possible to get so cold that you’re in danger unless you are in the water for more than about 30 minutes.”

And here’s the chart showing that.  The vertical axis is time in water (in hours) and the horizontal axis is water temperature.


But now you say – wait, what about people who freeze to death in water in a matter of minutes?  Well… it turns out just ‘being cold’ is not really your biggest problemo.  What is actually your problem is one of two things – the shock your body gets with respect to breathing, where you breathing rate skyrockets temporarily – which in turn causes many people to actually drown from consumption of water.  The second, is simply a heart attack.

The below graph shows your breathing rate.  The horizontal axis is time in seconds, and the vertical is breaths/minute.


The real purpose of my post

So where am I going with all of this?  Probably not where you think.  No, I’m not recommending you go out in your partially frozen lake and go for a dip.

I’m actually about to share a little secret for triathlon’s that some first timers may not realize (well, they will after their first time).  You know how before the swim leg you see all of those folks out there in the cold water doing short laps and warm up?  That’s not all about warming your muscles up and looking special.  It’s about getting your breathing calmed down. 

Why does it it matter?  Take a look at the above graph.  This is just if you drop someone into the water – no active swimming or battling that occurs during the first 1-2 minutes of a tri.  Note that it takes 40-50 seconds to ‘compose yourself’ with respect to breathing in the above graph.  In effect you’re breathing will be MORE THAN DOUBLE what it needs to be before you add the tri madness.

Try it sometime.  Go into an open water swim (race or training) and swim for about 30-60 seconds first.  Then stop, let your body calm down.   And now go out and swim for ‘real’.  Feels a lot better, doesn’t it?

If I had one recommendation for first time open water swimmers – it would be to take advantage of those few minutes to get accustomed to the water and let your breathing calm down – even if it means just sitting in the water.  That way you’re not out of breath and drowning 90 seconds into your tri.

And remember the rule of open water swims – if you EVER get in trouble, simply roll over on your back and just float until you’re calmed down.  You’ll feel fine within 10-15 seconds and be ready to continue on.

As an aside, a surprising number of folks have e-mailed me about open water swimming in the DC area over the past few months.  I did make one post a while back about it – but I’ll revisit it with a comprehensive guide in late March once the weather warms up a bit.  As always, feel free to e-mail me with any questions – I’m more than happy to help.


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  1. Good post!!

    Another thing that happens with novice open water swimmers is when that hyperventilation begins they freak out and freeze or bail out and blame themselves for being unprepared and all sorts of bad things – I wish more people would spread the word that this is simply a predictable physiological response and the secret is to get your face in the water early for a long warmup to get it over with before the event begins.

  2. Wow. I didn’t actually know this. I hate getting in the water–I absolutely hate the cold. I usually put it off as long as possible, which means in a race I don’t warm up…
    very interesting…

  3. here in cali, it was 80 yesterday, a little cooler today. water temp in the pacific here is 57-59. still a bit nippy, but warm enough if i wear a hood and maybe booties and maybe wait ’til about noon to start. i’ll let y’all know how it went for sure.

    • Ashley Huber

      hehehe I appreciate where you’re comming from as we are a creature of our conditioning (example I would be dying in 80 to go for a swim due to over heating) but I swim in a lake that only averages between 34 and 55 in the peek of summer. No I wear no gear, not even a swim cap or googles most casual swims.
      I love how different we all are, but still so the same!

  4. penguins and water seals look so happy.

    Cold water doesn’t freak me out…its those first few strokes when the head is in the water.
    after that..everything is fine…

  5. wow, i had no idea. this is a great tip, cuz i’m sure i’d be one of those people hyperventilating and probly giving myself a heart attack. like nancy said.

    warm up!

  6. teresa

    I have a question…i am 57 and for years i have swum everyday,,at seven…during the warmer months maybe for half an hour but as it gets colder just for 15 mins….usually i roll out of bed at 6.45, put my togs on and i’m in the water at seven…I don’t do anywarm up exercise and to date i have been fine…but, for the past month as it has got coldder i feel fine while i’m swimming but later in the day my upper torso, shoulders and arms are aching……any clues???

  7. Hmm… I’m honestly not sure. The question is – is it the water, or some other factor. I’d be interested in seeing if you went at the same time of the day to a local pool and swam the same distance if you’d have the same issues. That way you could rule out cold water. Time of day is somewhat important because your body reacts differently depending on the time of day.

  8. newtotri

    Hmmm… I wish I read this before my first tri. The first couple of minutes were the worst I have ever experienced while swimming. The combination of the water temp, excitement, starting a bit too fast, contributed to feeling like I couldn’t keep my head under water for more than one stroke. It of course got better, and I settle down, but it was a very rude welcome to the tri world for me. To Nancy’s point, I thought I was pretty well prepared but all of a sudden I started having second thoughts… well at least for the first couple of minutes.

  9. Michael

    I know this is an old thread but i’ve just stumbled on it while discovering your excellent reviews and then moving onto the ’25 most useful articles’.

    Please just be aware of the DANGER in the statement “if you keep moving and keep it to about 30 minutes you’re in the safe zone”. This very much assumes either a wetsuit is in use or the water is only a bit cold like 10 degrees maybe.

    When you swim in cold water your body protects vital organs by reducing blood flow to the skin & limbs. The core stays warm while the skin, arms and legs cool down. The process is known as peripheral vasoconstriction.

    Your limbs will grind to a halt and you won’t be able to keep moving….likely somewhat before hypothermia is an issue you’ll just drown.

    My own practical examples; In January I was swimming between 25 and 45 minutes in a tri-suit in our 5 degree sea twice a week. I’d been in the sea at least this often every week since October when I transferred into a wetsuit at the end of summer and temp’ was heading towards single figures. Also in January I took 2 swims without wetsuit. The first of 6 minutes was fine. The second of 14 minutes wasn’t. After 12 minutes i’d credit my swim buddy for keeping me calm, focussed & moving in the right direction because alone I was losing control. At the same time a more experienced skin swimmer in our group who regularly did 18-20 minutes pushed that day to 24 and had a similar experience to me. So it only takes a couple of minutes to go from ok to not ok.

  10. Irving Bissell

    if you have clothing on you will loose heat slower if you ball up and dont move at all. your shivering will keep your muscles producing heat. if you move in cold water you replace the thin layer of warm water surrounding you with cold water creating faster thermal loss. of course if you can swim to a place where you can get out of the cold water, do so, since water immersion is the fastest way to cool or heat a body.

  11. Good article Ray!

    Even for experienced athletes I think that the part that a lot of us dread the most is not the burning legs at the end of the bike, the “I can’t take another step and I’ve still got two more laps to go” thoughts on the run, but just getting in the water BEFORE the race.

    I know I’ve been there and done that, and the fine fellas at the Tower 26 podcast discussed just this on a recent episode.

    Anyway, getting some hard data like this can help make it a bit easier for all triathletes to do what you gotta do and get in and warm-up before the race, so thanks for putting it out there!

  12. Wondering how people can withstand those low temperatures. Currently, there is an ongoing cold water swimming competition at 35 Fahrenheit cold water (2° Celsius) in my hometown. For me this is really crazy. I mean even just entering the water at these temperatures might give me an instant shock. Not to talk about swimming.

  13. TriAlan

    Waking an old thread, sorry :)
    Any experience on here of SIPE* – I got hit with this at Helsingor 70.3 last summer, ended up gasping for breath and later coughing up blood. How to avoid this?

    * Swimming Induced Pulmonary Edema