Benefits of Cold Water Swimming - By Jono Ridler

As I write this, it is less than 5 days until we officially enter the New Zealand winter swimming season. Around the country, open-water swimmers have felt the water cooling from the precipitous highs reached during the recent summer; the cold bringing a sense of excitement for some and dread for others. Personally, I fall strictly into the camp of the former. This will now be my fifth season of winter ocean swimming non-wetsuit, since ditching the rubber in the winter of 2018 to build cold adaptation in the lead up to my successful crossing of Cook Strait in the summer of 2019. I’ve since completed a number of other long-distance cold-water challenges, including an ice-mile (a mile of swimming in temperatures less than 5 degrees Celsius) in the Canterbury alps in 2021.

Cold-water swimming brings with it a number of physical and mental health benefits that are not easily replicable in warmer waters. If you are a fair-weather swimmer or a pool junkie, I unashamedly hope that this article tempts you to dip your toes (and potentially a bit more) into the embrace of the winter ocean or lake.

Improvement in mood

Swimming in cold-water has been found to activate the sympathetic nervous system, increasing the concentration of dopamine, serotonin, norepinephrine, and β-endorphin [1,2]. Anybody who has been cold-water swimming can relate to the sensation of the “post-swim high” – an improved mood and sense of wellbeing that follows from the event. In my personal experience, this high can often last through the duration of the day.

In some cases, cold-water swimming has also anecdotally led to a decrease or elimination in the symptoms of depression. In one popularized case, a 24-year woman with symptoms of severe depression was able to discontinue medication after following an intervention which included weekly cold-water swimming for a one-year period [1]. While there is limited research on the topic, I certainly have come across a number of stories that back this up.


Swimming in its broader form is a fantastic method of “active mindfulness” – defined as an introspective state of consciousness (or a concentrated awareness of body and mind) while in a state of movement. The act of moving yourself through the water with the highest degree of efficiency demands your attention on a wide range of bodily elements simultaneously – the feel of the water, your body position, the timing of your breath, the interplay between the kick and the stroke, and so on. Personally, I also find that the more strenuous the workout, the higher the degree of presence and awareness in the moment; I am unlikely to be thinking about the challenges of the day ahead if I am a few degrees of separation from vomiting!

The same can be said of cold-water swimming, which brings you into your mind and consciousness to an extent that swimming in warmer waters does not. When the experience of dipping or swimming in cold-water is beyond your comfort level, you are brought firmly into your mind and body through the physical sensations you are subjected to, forcing concentrated awareness and thus mindfulness. Mindfulness, generally speaking, offers a number of fantastic benefits, including stress control and improved attention [3].

A sense of satisfaction

Cold-water swimming is not easy. It requires you to reach beyond your comfort zone, particularly as you are first starting and have little in the way of natural adaptation. I remember during my first season of swimming through winter non-wetsuit, I would push myself beyond the outer ranges of my capability in attempt to, in theory, shortcut the adaptation timespan, experiencing relatively severe post-swim reactions certainly symptomatic of moderate hypothermia (read: this is not the safest route!).

Although this could be described as dangerous, stupid, or any number of choice words, I would end every swim with a sense of accomplishment for having achieved something difficult; something that I previously perceived as outside of my limitations. Even now, after years of swimming non-wetsuit, in temperatures and of a duration that would be considered extreme anywhere in the world, I feel a unique sense of satisfaction after completing a cold-water swim. Cold-water swimming is not easy, but it is certainly rewarding.

General resilience

While cold-water swimming may build the physiological ability to withstand temperature deviations (in and out of the water), in my experience it also builds the ability to withstand the pressures of everyday life. If you do something difficult, repeatedly, it tends to have an expansionary effect on your perceived comfort zone. Swimming every week through winter in the nearby ocean or lake as the temperature drops is not comfortable, nor is it easy. Your comfort zone will grow to meet the widened personal expectation that you create and reinforce through your repeated behaviour. As you do one thing that is hard, it has somewhat of a cross-over effect, making other things that may have been previously perceived as difficult feel less so.

For me personally, I see this evident in my ability to withstand difficult situations at work. It is also a two-way street; while expanding my comfort zone through cold-water swimming increases my ability to navigate the stress induced by work, so too does the difficulty experienced in the workplace aid my mental endurance while cold-water swimming. As the saying goes: Do the hard things until the hard things become easy.

I hope that has provided somewhat of a convincing argument to give open-water swimming a try this winter – whether it be in a wetsuit with all the accessories or braving the elements non-wetsuit. It would be remiss of me not to end with a note on safety. This article really hasn’t touched on any of the risks related to cold-water swimming (yes, these exist), so please do your due diligence before you set off. And always, always make sure to swim with somebody else when you are swimming in cold-water.

See you in the ocean!


1. Knechtle, B; Waskiewicz, Z; Sousa, C.V.; Hill, L; Nikolaidis, P.T. (2020). Cold Water Swimming – Benefits and Risks: A Narrative Review. International Journal of Environmental Research and Public Health, 17.

2. Tipton, M.J.; Collier, N; Massey, H; Corbett, J; Harper, M. (2017). Cold water immersion: kill or cure? Experimental Physiology, 102(11), 1335-1355.

3. Davis, D.M.; Hayes, J.A. (2011). What Are the Benefits of Mindfulness? A Practice Review of Psychotherapy-Related Research. Psychotherapy, 48(2), 198-208.

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