Getting into cold water – acclimatising and having fun
At the start of race season, as thoughts turn to open water swims, one of the key considerations is, just how do you swim comfortably in cold water. In this article Coach Denise uses her extensive experience of swimming in Scotland to look at how best to make the transition from the pool to outside, helping you to have the best swim leg you can.
For many triathletes, especially the less experienced, one of the biggest areas of concern is the swim. A large proportion of triathletes do not have a swimming background, and even those that do typically come from a pool swimming background. While open water swimming has increased in popularity, getting into open water to swim is not something a lot of people have done regularly. There are a number of concerns people have, it’s cold, it’s dark, there might be things lurking in there, how do I swim in a straight line and so on.
One of the critical aspects is the fact that most of the time in the UK the water outside is significantly colder than in a swimming pool. Like any fear, learning about it can reduce the concerns and help you embrace your inner mermaid.
Firstly, let’s think about how cold is cold. According to the RNLI, anything below 15°C is defined as cold water and can seriously affect your breathing and movement. Average UK and Ireland sea temperatures are just 12°C. Rivers such as the Thames are colder - even in the summer.
If you are not used to swimming in colder temperatures there is a risk of cold water shock, the symptoms of which have also been clearly described by the RNLI.
Cold water shock causes the blood vessels in the skin to close, which increases the resistance of blood flow. Heart rate is also increased. As a result the heart has to work harder and your blood pressure goes up. Cold water shock can therefore cause heart attacks, even in the relatively young and healthy.
The sudden cooling of the skin by cold water also causes an involuntary gasp for breath. Breathing rates can change uncontrollably, sometimes increasing as much as tenfold. All these responses contribute to a feeling of panic, increasing the chance of inhaling water directly into the lungs.
Looking at the above two statements, it would be easy to think that entering any body of water in the UK is dangerous and should be avoided.
In practice, there are a number of factors to consider which make it perfectly safe to enter, and stay in, rivers, lakes and the sea for some time.
These factors include acclimatisation, choice of clothing and swimming rate and ability.
Let’s take a look at acclimatisation first. This has two main aspects – the immediate and the long term. By immediate acclimatisation I mean that on entering open water your body can react differently on any one day due to a lot of factors. So each time you go into open water give yourself some time to adjust to the temperature of the water. Even if you are going into an area of water you know well, think about how it is that day. Recent rain fall can drop the temperatures of loch’s and lakes quickly, sun on the water, especially if it is shallow, can raise it fast too. Sea water temperatures tend to be more stable and rise and fall more slowly.
Enter the water slowly, putting your hands into the water up to the wrists and splashing water around your neck area. Blood is close to the surface at the wrists and the neck, so getting these areas used to the idea of the lower temperature quickly will help. Also, body adjustments to temperature are regulated by the hypothalamus in the brain. The hypothalamus will respond to the temperature of the water coming into it and this is mainly the blood from the neck area.
As you get in deeper the water will enter your wet suit through the zip. This initially feels cold but will warm up quite quickly. Moving around will help a lot to generate heat and warm this water up faster.
Once water is in the wet suit a few strokes of breaststroke can help to get more acclimatised, and then its time to get your face into the water. Different people react differently to this. If you are somewhere you have not swum before, or you are feeling the cold, take this slowly. A few strokes of breaststroke with face in and out of the water can help. Otherwise, try taking ten strokes front crawl, and then stopping to see how it feels. If you have any nervousness about this then take these stages in water where you can easily stand up.
Another important consideration as you enter the water is your breathing. In any stressful situation, the body triggers a fight or flight response. Part of this response is to elevate the breathing rate to increase the supply of oxygen to the muscles ready for the fight or flight activity. As the breathing rate increases it can also trigger a panic reaction. This impact can be reversed by controlling the breathing. Taking deep breaths, long and slowly, sends a signal to the brain that all is well and reduces this fight or flight response. So, as you enter the water take long slow deliberate breaths to help to control both mind and body.
Longer term, regular swimming in cold water can acclimatise the body to the colder environment. I swim regularly in Scotland and the RNLI definition of cold water applies to most of the water here all year round. However, by swimming regularly outside I find I feel the cold a lot less than I used to. Personally, I find any water above around 8 or 9°C comfortable for swimming, with appropriate clothing, and can accommodate down to 5°C. By comparison I have been at events where triathletes, in wet suits, have been hypothermic after swimming in 16°C water, while I’ve been thinking it was super warm.
Thinking about the appropriate clothing, most races will be wet suit compulsory or optional. The huge advantage of a wet suit, along with the buoyancy it offers, is that it makes the water feel much warmer. If you really feel the cold then thermal wet suits are also available, with thicker neoprene and added insulation. Another trick to reduce the cold water shock is to warm the water inside the wet suit. The traditional way to do this is to pee inside the suit, and many swimmers find the cold makes them want to pee anyway. If you prefer not to do this, then pouring some warm (not hot) water into the suit just as you get in will reduce the impact of the cold water entering the suit.
As described above one key area to protect is the neck and using a neoprene cap with a chin strap, worn on its own or under a swim cap, can really help to protect this region from the cold.
Goggle types vary a lot too, when racing it might be important to have streamlined goggles, but in training, especially early in the year, being warm enough in the water to get a good swim in is more important. Goggles which cover the bridge of the nose fully will reduce that ‘ice cream headache’ feeling that many swimmers experience in cold water.
While most races will not allow the use of socks, shoes or gloves, it is worth wearing these if you want to get as long a swim as possible before the water has warmed up. As a rule of thumb, the thicker the neoprene, the more insulation the item offers.
Having dressed appropriately and entered the water carefully, the final thoughts are around your swim ability and speed. Moving will warm you from the inside and so getting swimming as soon as you can is important. A strong swimmer will generate more heat than a slower one, so can possibly stay in the water longer, though other factors are also important. Doing a quick body check at intervals is a good idea to see how you are feeling. A quick exercise to determine if you are getting cold is to touch each finger to your thumb in turn. If you start to find this hard, it is a sign that you are getting cold and should think about getting out.
However long you swim, and regardless of how warm or cold you feel, it’s always a good idea to have a flask of a hot drink close to hand and have some of it as soon as you get out. This will warm you up from the inside as well as being the perfect accompaniment to the well-earned ‘shivery bite’.
Getting comfortable in the open water can take a few goes, along with some trial and error, but it is massively rewarding. Not only can it give you an advantage on race day, but it can also mean you can build the confidence to swim in some truly beautiful locations, though always with a friend.
Denise has been coaching triathletes since 2019 as a coach at her local triathlon club in West Lothian. Between 2019 and 2022, Denise was the Head coach in the club, working with a team of coaches to support and develop triathletes with a wide range of capabilities, completing her BTF Triathlon Level 2 coaching qualification in 2021.
Denise joined Tri Training Harder as a coach in 2021, building on the qualifications through the experience and knowledge passed on by the coaching team.
In 2019 Denise set up and continues to run her own Jog Scotland running group, a mixed ability group of runners who meet weekly. This delivers on her passion for helping people to do much more than they think they can.
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