Acclimatisation to the cold

 Acclimatisation to cold water.

If you are planning to swim the Channel then along with training for a long distance swim you will also need to acclimatise to swimming in cold water. There is both a physiological side to this, namely swimming in water that is much colder than a heated pool, and also the fact that you are out swimming in open water, which in itself is a completely different experience to swimming in the pool. These two elements are distinct but also overlap quite considerably in the challenges they pose.

 The fear factor

There are clearly many differences to swimming in open water but some of the main ones are the possible lack of visibility, waves and movement of water around you, all sorts of marine life around you and perhaps the main one being a general fear of the unknown. There is already a deep fear instilled in us of being in the sea, as played up on in films such as Jaws, but also just being immersed in the water seems to change our whole perceptual awareness of our surroundings. What looks like a friendly looking sandy cove from the beach suddenly takes on a whole new dimension as soon as we put our toes in the water. Dim outlines of rocks underneath us or tiny bits of seaweed brushing against us turn a refreshing dip into a sprint for the shore to escape the vicious man-eating shark that our minds have conjured up. It’s probably similar to seeing a quaint old house in the afternoon sunshine and then lying wide awake at night in one of its rooms sensitive to every tiny noise and imagining the whole place to be haunted.

I realised how psychological all this was when I experienced the same fears when swimming in a small swimming pool once. As I swam up and down an image came to me from the James Bond film where the villain has a trap door in the side of the pool and lets a pair of ravenous sharks swim into the pool to entertain the swimmer. Of course a little fear is important and a biological necessity to make sure we don’t swim where there may be genuine danger but it can take quite a while before we feel at home in the open water and not prey to irrational fears. So in some ways quite a fair chunk of the training in open water, as well as being about getting stronger and building up to swim further as we might do in the pool, is also about overcoming fear. There’s no doubt that when we manage to overcome these fears we seem to get tremendous energy and that as long as the fear is still there our natural energy is a little blocked.

 The cold factor

As discussed, the fear factor and the cold factor both overlap to some extent, as fear of the cold increases the other fears quite significantly. It seems that most of us have had some kind of experience as children of going swimming in the sea or in a lake or river somewhere and just remember it as being icy cold. Our instinctive reactions when looking at the sea or any open water, especially in colder climates, are that it must be freezing cold and the general reaction of people seeing you swimming there is the ‘isn’t it really cold?’ or ‘rather you than me’ response. The bottom line is that it really is not nearly as bad as you might think! Not only is it generally not that cold but it is also amazing what the body can adapt to in a relatively short space of time. The hardest thing is the first few minutes, which even when the water is not that cold are always a shock to the system. Once we are in and fully immersed, the brief stinging pain gives way to tremendous joy and a refreshing feeling that stays with us for a long time. These feelings of health and well-being that we get from sea swimming are attested to by the growing numbers of ‘wild’ swimmers and winter sea swimmers.


Personally I am a great advocate of entering the water very slowly and getting the body used to the change gradually. I will typically walk up and down the beach for some time just up to my ankles before slowly going in a bit deeper, perhaps just up to the top of my thighs. Having reached the stage where I’m comfortable with this and my breathing is fairly relaxed I will wade in so that the water is up to my middle and just wait a minute or two until the breathing is under control again. The next stage is to get the body fully immersed until just your head is out of the water and then finally, and if it is winter time the hardest part, putting your head under the water a few times until you feel comfortable swimming a few strokes. Having gone through this build up you will then feel very at ease in the water and start to enter into what I think of as the blissful and refreshing stage. Of course those of a more daredevil disposition will probably want to run down the beach and jump in, which I think is probably absolutely fine too. The only thing to be said for the slow approach is that it gives the system a bit of time to adjust.

 Once you are in the water and swimming about, the body’s miraculous ability to acclimatise starts to kick in. You will probably find that once in you are able to stay in a little longer than you would ever have anticipated, but also if you start doing it regularly you will be amazed at how quickly the body adapts. If you can manage ten or fifteen minutes the first day then before long you will find that you can swim for three-quarters of an hour to an hour with no problem. Once you reach that stage then you will find you can build up to an hour and a half and eventually two hours. Once you can swim for two hours then it will only be a matter of time and a matter of your level of dedication before you can start building up to doing the longer swims necessary for preparing for the Channel, should that be your ultimate goal. Following the techniques suggested above it should be possible for anyone with average health and strength to swim for a short while in water temperature of thirteen degrees and above. Personally I find I can now swim in the winter in the UK when the sea temperatures get down to about eight degrees but I think that is after a number of years of building up to it. There are of course some hardy souls who have swum in much colder water, even Arctic temperatures and you might like to take a look at some of the achievements of Lynne Cox and Owen Gordon Pugh.

 The main thing to stress is that most of the battle is in just getting yourself immersed in the water. It’s hardly surprising the body finds this a shock as it is just not something we really ever do normally. Having said that, once we do start, it is amazing how quickly the body starts learning to adapt to it. For some reason this does not seem to change the sensations of the first five or ten minutes whilst we are slowly entering the water. Even if I have been going in regularly over the winter with temperatures down to eight degrees, when I enter the water in September (the warmest month for sea temperatures) with temperatures up to fifteen degrees or so, I still feel the same slightly painful stinging sensations until I’m finally immersed. The acclimatisation perhaps has built in to me the knowledge that in a few minutes I’ll be enjoying it and also will have prepared me for staying in longer. Coming back to this memory or fear that we all seem to have that the water will be freezing, it’s probably because we never went past the painful part to the enjoyable part, so our minds forever associate it with being freezing and miserable. If I tell someone that I have swum for an hour in the sea they will imagine that the whole hour was spent suffering that intense feeling of cold. Nothing could be further from the truth as it would only have been a couple of minutes that were like that before the body adjusted to the stage of actually enjoying it. The other point is that once you are in and swimming, you move around vigorously so you then start to generate heat. It is rather like going out on a cold day perhaps dressed only in a t-shirt. You may feel uncomfortable but if you start moving around then you warm up quite quickly and in fact probably don’t want another layer on after all. That brings us back to the only real conclusion and that is that it really is not nearly as bad as it seems!

 Dressing for the occasion.

As discussed elsewhere the Channel swimming regulations only permit standard swimming costume, goggles and cap. The key element here is the swimming cap. We lose almost eighty percent of our body heat through our head, so it is essential that you wear a good silicon swimming cap (silicon caps are thicker than the ones people usually wear in pools). Actually the trunks or costume are probably important too, but from the point of heat loss the cap is the main thing!




7 Responses to Acclimatisation to the cold

  1. stephen says:

    Hi,great article,I have been thinking about winter swimming in the. northsea for years but have been put off by the scare mongers who tell me about the dangers of sea swimming in freezing conditions after reading this I am just going to go for it so have you anymore advice for me,kind regards stephen

    • Karteek says:

      Hi Stephen

      I admire your enthusiasm! To be honest between now and the end of March is probably the coldest time of year in the North Sea so you are brave to start now. Like I said I think it is much safer and more pleasurable to enter the water slowly and particularly if you have not been in much in the winter before. Just give your body some time to adjust to the change in temperature. After about the beginning of November I usually use some small wetsuit boots and a pair of swimming gloves. This really helps keep the extremities warm and as long as you are wearing a good silicone cap should make a big difference. As you enter the water and start wading around you’ll find your breathing naturally gets a bit deeper and the further in you’ll find your body forcing you to breathe more deeply too. Once you are fully in and start to get used to it a bit you’ll find your breathing becomes much more relaxed. I really don’t think there is anything to worry about but maybe it would be good to have someone else around the first few times and of course if you have any medical condition or heart issue then you should check with a doctor. Also you can remind yourself that it may seem ‘freezing’ but it is not actually freezing like your friends say. It is probably somewhere between 7 and 10 degrees celsius which is not that much different from the outside air temperature during the day. Thanks for getting in touch and let me know how it goes and if you have any other questions. Karteek.

  2. Margie says:

    Hi there,
    Do you know of any resources on the internet about acclimatising for cold water swimming, when you have no access to a cold body of water? ie no pool cold enough and no lake or sea cold enough nearby?? Are there alternatives] ways to get your body ready for the cold temps?

    • Karteek says:

      Interesting question. I’ve read somewhere that it might be good training to keep your feet in a bucket of cold water from time to time but have never tried it so hard to comment. Other people take cold showers and wander around in thin t-shirts outside when the weather is cold. I’m fortunate enough now to have the sea quite close by so it is not so much of an issue but for many years I didn’t start any cold water acclimatisation until a month or two before a swim. I’m not so much in favour of just letting the body get cold in a rather static way and hoping that it will somehow make you more resilient to cold water because it seems that the way we deal with the cold is in an active and dynamic way. You enter into the cold water and jump up and down, flail your arms around or generally move quite vigorously to generate heat. Recently I’ve been finding that breathing exercises are the best way for strengthening the system and getting it ready for the cold so I think that would be my best suggestion.

  3. Ed says:

    I am planning to do a channel relay in Aug 2017. I have a lake about 14 miles away that will start to get quite cold in the next few months. But 2 miles away i have a weir from a chalk stream, a bit like an endless pool, it stays at 10-11 degrees c all year. I think this is too cold for me to get used to cold water at first, but I am considering wearing neoprene shorts and sleeveless vest. I even get cold in the swimming pool when supervising my 3 yr old!!! So neoprene vest-good idea???
    As I will only be in for 1 hr at a time-what is your advice re fattening up also…

    • Karteek says:

      Hi Ed.

      My apologies for the delay in getting back to you but I completely lost touch with the site for a long time. I’ve no idea if a reply is even still relevant. Please feel free to email back though and will be checking now regularly.

      Am sure you are well on your way to knowing what to do by now but anyway here goes. Well the chalk stream sounds amazing but you are right it might be a little cold for you. Even going in just for a few minutes though can be very beneficial. Don’t worry that because you will be in channel for several hours a few minutes is not useful – I think it is really good for the body and you will feel great after it. But no problem to use the neoprene – especially a thinner one. A lot of it is just getting used to going into ‘wild’ water or non swimming pool water. It seems to be quite a step for the mind. You might find that after a while you are inspired to try without.

      I’ve never really deliberately fattened up – I just find that in the last few months before a swim I end up eating a lot more after doing the longer cold water swims. That’s partly a physical thing and partly a psychological thing I think. A lot depends on your metabolism and body type. Thinner types can definitely benefit from consciously trying to eat a little more even though that might be quite tough.

      The key think will just be to make sure you are happy swimming for an hour or more in the sea. It’s really worth making sure you are totally comfortable with this as sometimes relay attempts can fail just because one or two members get cold and sea sick on the boat. So plenty of acclimatisation to the sea and colder water is good. Of course you need to swim more than an hour altogether so maybe is best to be comfortable doing 2 hours non-stop in the sea.

      Hope it is of some help and sorry for the delay! I’l be able to get back much quicker now. Let me know how you are getting on.


  4. Pingback: Adaptation to cold: habituation and acclimatization | wildbigswim

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