Where to swim in cold water, what to wear, the benefits, the risks and how to prevent them

Author of The Cold Fix, Sara Barnes, answers frequently asked questions about swimming in cold water.

Cold-water swimming is typically when you swim with no neoprene in water that is 15C and below. Above that temperature the body can withstand the cold more effectively and for longer. However, care still needs to be taken with regards how long you are in the water for, how you warm up and checking for delayed symptoms of hypothermia. In the UK, our inland waters rarely go above around 22C except in shallow bodies of water, such as manmade lakes. For example, in the Lake District, the lakes are deep and take much longer to warm up. The warmest temperature may reach around 21C, but that is usually only in the top six feet of water. Temperatures decrease at greater depths, so great care needs to be taken when attempting to swim longer distances, or across lakes as temperatures may vary considerably further from the shore in deeper water.

What are the medicinal benefits of cold water swimming or cold water immersion?

It is now well documented that there are numerous physical and mental benefits to regular cold-water swimming and immersion. The most obvious physical ones are improved blood circulation from repeated constriction and dilation of blood vessels all over the body, but in particular the heart; improved skin and muscle tone due to better blood circulation; improved tolerance to variations in ambient temperature in everyday life, which tends to increase motivation to be outdoors or even turn the heating down at home; release of good hormones such as endorphins and oxytocin, which in turn counteract the release of stress hormones such as cortisol; and increased natural immunity to infection and viruses.  The mental benefits possibly outweigh the physical ones. One of the overlaps is related to the increased release of positive hormones such as oxytocin and endorphins, which are the feel good hormones that are responsible for that sense of exhilaration post swim, equivalent to the runners’ high. Repeated and regular immersion can extend that flow of positivity and generally improve someone’s mood and sense of wellness. The cold water is also known to reduce inflammation in the body in general, which is why it can act as a physical pain relief. When this occurs in the brain and nervous system it can have a major impact on a person’s mental health.

Is cold water swimming good for anxiety and depression?

Studies have shown that if someone regularly swims in cold water symptoms of anxiety and low mood, or in more severe cases, depression, will abate over time. This is a positive outcome that goes beyond the initial swimmers’ high and can have life-changing consequences.

What are the risks of cold-water swimming? 

This can vary from person to person, depending on their overall physical and mental health. It is advisable to have a general health check before embarking on regular or extreme cold-water exposure, just to make sure your heart is in good condition. Cold-water immersion puts your body under extreme stress, which can cause your heart rate to increase rapidly, so if you have high blood pressure it may be advisable to take things very gently until you have built up a tolerance to colder and colder water. If you are in good health and build up your tolerance gradually over many weeks the risks of cold-water swimming can be minimised, providing you follow a sensible plan that suits you as an individual and this will vary from day to day, location to location and according to weather conditions. Always check in with yourself before getting in the water. How do you feel emotionally and physically? How much sleep did you have the night before and was it of good quality? Did you consume a lot of alcohol? When did you last eat? Are you fit and well as far as you know? All these factors will affect how your body copes with cold temperatures. As the water temperature drops it is even more important to make sure you have an easy access and exit route. Check your exit route before you get in the water and be prepared to change location if it doesn’t feel right. The risks of hypothermia are real even if you are experienced. Do not be tempted to stay in longer than usual just because you are chatting with someone who typically stays in longer. Swim your own swim. Get out before you start to feel warm and relaxed and don’t hang around in a wet swimsuit. Always have a hot drink when you get out and then start to get dressed, top half first and put on a bobble hat to keep warmth in.

When is it too cold to swim outside?

In my opinion it is never too cold to swim outside. The one factor that will make a huge difference to how cold it feels is the wind. Wind chill presents one of the greatest risks to swimmers, even on a fairly warm day. It will strip residual heat from your body within seconds and it is important to protect yourself from the wind by sheltering behind a wall, pulling on a microfibre changing robe or swim cloak as soon as you leave the water. It is sometimes warmer if you keep submerged rather than standing up and faffing about in the water. And when it is time to get out, get out quickly, but steadily. Do not hang about letting the wind chill you down. Snow and ice are cold, but static. Sometimes the water under the ice actually feels warmer than when the lake is not frozen over. But remember that getting out of ice takes longer and saps your energy more quickly. And ice can cut you without you realising it because your legs and arms are so cold you don’t feel the abrasion until your body has warmed up. So, don’t rush out through broken ice, walk gently and push the ice gently away from your body.

How long can you swim in cold water for?

There is no hard and fast rule about time and it varies from person to person on any given day. The best advice I can give is to build up the time very slowly. I tend to listen to my body and err on the side of caution every time. There is actually no need to stay in the water for any longer than two minutes to reap all the health benefits, so think in terms of how you feel rather than trying to stay in for longer. Remember that your core will continue to cool down for some time after you get out. The blood starts to flow back into your cold extremities and then back through your heart. Your core temperature can drop by a couple of degrees just through this continued cooling. 

How do you prepare for cold water swimming?

I think much of it is to do with state of mind and the desire to experience the cold. Cold showers for weeks before going into the water are sometimes recommended, but I can’t think of anything worse! And having a cold shower is NOTHING like walking into cold water. One of the best things to do is to go along to any group swims in your area, watch what other people do, talk with other people, gain as much information as you can about everything to do with cold water swimming. Then, go and find some cold water, preferably with a friend or onshore spotter. I usually swim alone, but if I am alone I never go out of my depth and I usually actually don’t swim, but just sit down in the shallows and enjoy the feeling of being immersed and still. If you want to swim distance in cold water then it is probably advisable to make contact with a local group and find someone who is prepared to swim by your side until you have a good grasp of how your body reacts to the cold. Just take it slowly whichever way you go, listen to your body and learn how to calm your brain. Make sure you have a hot drink, a few warm layers to put on afterwards, some neoprene gloves and swim socks, a towfloat and a bobble hat. There is a plethora of swim kit available now and the choice can be overwhelming. When you start out there is really no need for anything other than swim socks and gloves, swimsuit, a bobble hat, a thermos and a few easy-to-pull-on layers with a big warm coat on top. A towfloat is a very useful safety and reassurance device, which ensures you can be seen in the water easily and you can hold onto it if you get cramp or just need a brief rest. But it is not a flotation device and do not be tempted to swim further or faster just because you have one.

How do you get used to swimming in cold water?

It takes time and determination. Listen to your body. Go with different people to different places at different times of day. Do it at least four times a week to build up your tolerance reasonably quickly. If you can only swim once a week consider buying one of those pop up tubs that you can keep in your back garden filled with cold water. Sit in that every day if you can’t get to the lake or river.

How do you prevent cold-water shock?

Cold-water shock is when you take a gasp in the water. It is a natural reaction to the cold, but it only takes a pint or so of water to flood your lungs and you can drown. The best thing to do when going into the water is to take an in breath while you are walking in and then breathe out as you immerse. Only start to swim forwards once you are sure you have your breathing and heart rate under control. I often advice new swimmers to close their mouths when they dunk down. This has the effect of forcing them to breathe out through their nose and once in they can start to breathe normally. It also calms you down and stops you talking and panicking.

Is it dangerous to jump into cold water?

It can be even if you are acclimatised to the cold. There is quite a lot of media panic about this though, so be aware that some people will choose to jump in, but they are experienced and seasoned cold-water swimmers. Again, it is vital to take a breath in as you jump to avoid cold-water shock or gasping as you enter the water. It is actually a good idea to dunk first or have a brief swim before considering jumping or diving in because your body will be prepared for the cold. I would advise not to jump in your early experience as a cold-water swimmer, but by all means don’t rule it out as you get more experienced and in tune with how your body reacts on any given day.

What does cold water do to your muscles?

Your muscles can tire more quickly when the water is cold and you will find that your arms and legs start to slow down. Also, the blood starts to leave your extremities and arms and legs and retreat to the core, so there is less oxygenated blood to work the muscles. You can get cramp more easily in the cold water too, which is something to be alert to. A towfloat can be essential if you get cramp.

Does swimming in cold water burn more calories?

Not necessarily. It burns brown fat, but not the unhealthy kind of fat. You would have to do an awful lot of swimming in cold water for there to be a noticeable difference. Plus, we all tend to crave a sweet snack after being in cold water and cake is not calorie free! I don’t know anyone who has actually lost weight by regular cold-water swimming, in fact, more people seem to gain weight.

What do you wear to swim in cold water and can you swim without a wetsuit?

You can wear a wetsuit if you like. The choice is personal and depends on what you want to experience and how you react to being in cold water. A normal swimsuit is fine, along with neoprene (4mm is the standard) gloves and swim socks. A bobble hat is great too for keeping your head warm while swimming and definitely for afterwards. Skinny dipping is also perfectly possible, although in the UK there is an intolerance towards public skinny dipping, whereas in some Scandinavian countries, such as Denmark, it is permitted even in very public places like the swimming jetties in downtown Copenhagen. Contrary to expectation it is no colder to skinny dip. In fact, I find it far more practical especially on colder days because on leaving the water all I need do is pull on a changing robe, pat myself dry and get dressed. No hanging around pulling off tight swimsuits with tricky straps.

What are the best wetsuits for swimming in cold water?

This also depends on personal choice and budget. There are thermal wetsuits available but they do cost a lot. If you are planning on swimming longer distances during the cold weather then a thermal wetsuit is probably the way to go. Otherwise a standard 4mm open water swimming wetsuit will suffice. But remember you will still get cold in a wetsuit. It does not guarantee you can stay safely in the water for ever. But, it does buy you a little extra time and give increased buoyancy, but it is still a good idea to wear a towfloat for visibility and reassurance. You can also wear a neoprene bonnet with an under-chin strap. This helps keep your head warm if you are doing front crawl, but does not protect your face.

Can you recommend some spots to swim in cold water?

It depends where you live. There is an increasing number of venues where you can swim right through the winter. Places like this are bound by restrictions according to insurance though and many are still operating book in advance sessions only following the pandemic. Many of these venues are in the south of UK where there seem to be fewer natural swimming spots. For those seeking a more wild and liberating experience consider Wales, the Lake District, Scotland and Ireland. But, along with the freedom comes increased personal responsibility and accountability. There are no lifeguards in the Lake District for example and you categorically swim at your own risk.