The many benefits of cold water swimming 

The many benefits of cold water swimming 

By Dr Lis Kilcourse MBBS MRCGP, aka The Running Medic

Due to the lockdown and the closure of pools over the last year open water and wild swimming has become increasingly popular. Go one step further than this and this winter has seen a boom in people choosing to continue open water swimming through the winter months and take up cold water swimming. On a personal level, I started to open water swim over the summer both because of injury and as a way to spend more time outdoors. As someone who grew up swimming, I have always been confident in the water, but I had never done it outside. I had become bored with years of lane swimming so previously the idea of swimming again didn’t appeal that much. Open water swimming was different though; it offered a chance for me to see swimming in a different light without the pressure of lap times and the opportunity to connect with the outdoors. A running injury in summer 2020 and the continued closure of gyms had given me fewer options for how I could train, so I started to open water swim as an alternative way to cross-train. I was soon hooked! 

The increase in popularity of open water swimming has accelerated because of the appreciation that open water swimming can bring with it mental as well as physical health benefits. The evidence for this comes from both research and anecdotal data. Cold water swimming, in particular, has received attention recently because of television documentaries which showcased the open water swimming in the lidos in Hampstead Heath and a BBC medical documentary when cold water swimming was used as a form of social prescribing for a lady with depression. These case series have been supported by early medical research which suggests beneficial physiological adaptations that occur from repeated cold-water immersion.  


Swimming itself brings with it many health benefits, as well as being an exercise that allows physical activity without weight-bearing through the joints, making it accessible to people of all mobilities. The rhythmic motion of swimming itself can reduce stress because it allows your mind to switch off. Swimming in open water gives you the additional benefit of green and blue therapy; green being the positive impact on wellbeing by being out in green spaces, and blue for being in blue spaces (water).  

Firstly, cold water is known to reduce inflammation. Inflammation is associated with chronic diseases including depression, cardiac disease, and diabetes. Repeated exposure to cold water is believed to cause adaptation over time which lowers the stress (inflammatory) response. There has been some evidence to show that those who swim in cold water regularly have less of a stress response than controls; i.e., they produce less of the hormone cortisol in response to stressful stimuli. Next, we believe that cold water swimming releases the polypeptide hormone endorphin which is well known as the feel-good hormone; it is hypothesised that this is more so than compared with other sports, although the evidence for this is poor. Those who participate in cold water swimming regularly will describe the “swimmer’s high” which is the feeling of elation that comes after a dip in freezing water (and keeps many addicted and coming back for more)! 

Finally, there is some evidence that open water swimming can improve your immune system, with those who regularly partake in cold water swimming self-reporting lower levels of upper respiratory tract infections. The hypothesis behind this is that repeated cold water exposure increases the number of white cells in the bloodstream, the type of cells we need to fight infection and a consequence of this would be an improved ability to fight off viral/bacterial infections. 

These are the proposed physical benefits, but there are psychological and social benefits for cold water swimming as well which can be equally important in their impact. First, the sense of self-confidence that cold water swimming can bring. There is something empowering about being in the cold water, the ability to do something so out of the ordinary can help one increase their level of self-assurance. Second, when individuals swim in a group this brings with it a sense of community, we know that especially for those who struggle with depression this can provide an increased sense of wellbeing. Furthermore, cold water and open water swimming are done in nature, and we know that exercise in nature (blue therapy) enhances happiness.

So how does it make me feel? 

For me, open water swimming reignited my love for a sport I thought I had left behind. After years of swimming lengths of the pool, I had become bored with it and I took eight years off swimming at all. However, getting into the open water allowed me to see swimming again in a different light; one where I was out in nature and could feel free to explore more. I started over the summer when the water was warm, and with every swim outside I felt a sense of exhilaration. When winter and the second lockdown came, I continued to swim outside in the colder water, without access to a pool, I was able to get in the water for 30 minutes to keep my swimming up. I found the swims so refreshing, at a time of stress they brought me a sense of peace. Now, I must confess I have not braved anything more than a nippy 6.3C on Boxing Day, but I look forward to adventuring back into the open water once the temperatures increase.  

If you would like to find out more about open water swimming check out:  

  • Your local swimming club/council website, for local clubs and events.