Most mornings in February, the water at Pells Pool is about fifteen degrees, which might not seem like much until you’re standing on its edge and witnessing someone’s shoulders stiffen the moment they enter. Then it becomes something more akin to a decision rather than just a number. In a strange way, the whole story of what’s happening to outdoor swimming in Britain at the moment is that choice of whether to continue or to intentionally lower the rest of the body into such cold water.
The growth of outdoor swimming is no longer particularly noteworthy. Anyone who has attempted to reserve a time slot at a well-known lido on a Saturday morning is already aware of this. Less evident is how consistent the growth has been and how it no longer appears to be a pandemic-era fad but rather to be something more permanent. The Outdoor Swimming Society estimates that there are about 7.5 million swimmers in UK rivers, lakes, lidos, and seas. This estimate has been repeated so frequently in industry reports that it has begun to feel like common knowledge, even though it is unclear how precisely it was calculated.
| Category | Details |
|---|---|
| Trend Name | Outdoor and cold-water swimming |
| UK Participants | Estimated 7.5 million people swim in open water or outdoor pools |
| Growth Period | Surged from 2020 onward, sustained through 2026 |
| Notable Venue | Pells Pool, Lewes — oldest freshwater outdoor public swimming bath in the UK, open since 1861 |
| Typical Pool Temperature for Cold Swims | Around 15°C in managed lido settings |
| Reported Benefits | Improved circulation, mood lift via endorphin release, stress reduction, fitness gains |
| Key Risk Factor | Cold water shock, particularly for inexperienced swimmers entering unsupervised water |
| Supporting Organisation | Outdoor Swimming Society |
Lewes’ Pells Pool is a good place to consider this, primarily because it predates the trend by roughly 150 years. The pool, which has been open since 1861, is the nation’s oldest freshwater outdoor public bath. It has withstood floods, periods of disrepair, a section used as a makeshift ice rink, and at least one serious proposal to pave it over for a skatepark. That one was contested. The town repeatedly made the decision that it wasn’t willing to lose this kind of detail, which makes a location feel less like infrastructure and more like a tiny, obstinate institution.
The water hasn’t changed. What matters is who is prepared to participate and why. Ten years ago, cold swimming was associated with a hint of eccentricity that was only found in newspaper photos from January 1st and retired men dressed as budgie smugglers. Although that image hasn’t completely vanished, it has been supplanted by something more mainstream and clinical: cold water as a wellness tool, which is discussed in the same breath as ice baths, sauna circuits, and the larger cult of purposeful discomfort that has taken hold in fitness culture. It is another matter entirely whether that reframing is airtight from a scientific standpoint. It is difficult to ignore the cultural shift.
Some of the claims are supported by research, but it’s important to be clear about how much of it is preliminary. The claim that cold water swimming is beneficial for everyone is significantly different from the fact that it has been linked to better circulation and blood pressure readings in individuals who already swim frequently and are otherwise healthy. Given how unpleasant the entry itself can feel, it is likely why so many swimmers describe the few minutes following a dip as disproportionately good, almost suspiciously good. The endorphin response is real enough; the body does release mood-lifting chemicals in response to cold shock.
It’s difficult to ignore how frequently the heart is brought up by those discussing this. The British Heart Foundation and other organizations have begun to publish specific guidelines for swimmers with pre-existing heart conditions because cold water causes a rapid spike in blood pressure and heart rate, known as the “cold shock response”. That is a serious warning. For a significant portion of people, the same cold that is known to elevate mood can actually cause cardiac stress. Fear doesn’t sell memberships, so it makes sense that the wellness narrative tends to skip over this section. It is present, hidden beneath the happier coverage.
The commercial opening here has been noticed by pool owners more quickly than anticipated. Businesses that used to spend their winters draining and covering residential pools are now promoting the opposite: leave it open, allow the water to naturally cool after the heater is turned off, and you’ll have something akin to a private cold-water facility without having to purchase a separate plunge pool. The reasoning is fairly sound. Winter water actually requires less chemical treatment because chlorine degrades more quickly under summer UV, and filtration schedules can be significantly reduced without sacrificing water quality. It’s one of those infrequent instances where the more fashionable and less expensive options coincide.
Even though the advice is given with differing degrees of urgency, industry safety guidelines generally agree on the following points: start out slowly, don’t swim alone, keep sessions brief at first, and view the initial moments as the most difficult rather than something to get through. Flexibility swimmers are encouraged to dip in and out rather than commit to laps, which lowers the barrier for those who are curious but understandably cautious. Lidos that run organized cold swims, such as the Lido Ponty sessions in Wales that have become somewhat of a seasonal fixture, tend to incorporate this feature.
It’s genuinely unclear whether this becomes a permanent fixture of British leisure or, in a sense, cools off. Once the novelty wears off, trends based on wellness culture have a tendency to overcorrect. In the coming years, cold swimming may become as commonplace and unremarkable as a gym membership, losing its current prestige. There is another variation in which it simply continues to expand covertly, as Pells Pool has done, one obstinate institution at a time, long after anyone is still referring to it as a trend.
i) https://www.aqualeisurepoolsandspas.com/warm-water-vs-cold-water-for-swimming/
ii) https://your.eastsussex.gov.uk/2025/06/27/take-the-plunge-this-summer-with-cold-water-swimming/
iii) https://jolynclothing.co.uk/blogs/jolyn-clothing/cold-water-swimming-strenghten-your-body-and-mind
iv) https://www.theguardian.com/business/2020/oct/24/cold-comfort-uk-outdoor-swimming-venues-stay-open-to-meet-demand
v) https://www.countryfile.com/go-outdoors/get-active/britains-seaside-lido-revival-history-of-the-lido-and-best-places-to-swim