Cold water temperature varies hugely, and while this isn’t scientific, anecdotally, open water swimmers experience it in these bands.
Compared to indoor heated swimming pools, which vary in temperature from around 26 to 31 degrees Celsius, swimmers are likely to be exposed to a much wider range of temperatures when swimming outside. In the UK, inland waters can be as low as zero in winter to as high as the mid 20s in peak summer. Coastal waters vary from low single digits to the high teens. The water temperature has a massive impact on how you swim and how long you can safely stay in the water.
Jumping in is likely to impair breathing in the uninitiated, as breath comes in big jolting gasps and it feels like someone has clamped on an ice neck brace. Water has bite, skin smarts and burns. This is winter swimming. Limbs soon become weak – 25 metres can be an achievement – and only takes a minute or two at the lower end of temperatures before skin becomes a lurid purple-orange-red (for those with lighter skin) when you exit.
That said, the joy of swimming without a wetsuit at this end of the temperature spectrum is the cold water high: the pure exhilaration and rush of endorphins that you get from getting in. Winter swimmers frequently become addicted to it, and it is sufficiently powerful that a 1-2 minute swim can leave you feeling good all day. Anecdotally winter swimming clubs like Serpentine Swimming Club and Tooting Bec Swimming Clubs report increased immunity and fewer colds.
Much like baltic, but not quite so painful, or breathtaking.
At this temperature triathlons start operating. In a wetsuit you may find you can swim comfortably for a while, outside of one the water is fresh, doable for the brave, and not a problem for hardened open water lovers.
Lakes and more mature rivers reach this temperature over summer, during hot spells. Still fresh on entry, but comfortable picnic lazy-hazy summer swimming.
You’d think that’d be a good thing, but on the rare occasions that river pools and shallow lakes reach these temperatures during hot spells, there is the odd sense that there’s something missing…. the exhilarated feeling when you get out, that cold water ‘tang’. On the plus side, some of you will be able to spend hours swimming without a wetsuit.
Arguably unpleasant. Plus, as Rob Fryer comments, ‘the sun is not invited’.
When embracing cold water please be aware of the following – wearing a wetsuit keeps you warmer for longer, but will not protect you from these risks:
Kate Rew is the author of The Outdoor Swimmers’ Handbook (Rider, 2022, available internationally and signed in The OSS shop) and Wild Swim (Faber). Instagram: @kate_rew.