IIf you happen to know an outdoor or wild swimmer – and you’re reading them observer, let’s face it, you almost certainly do — you might have been particularly euphoric last week. The recent cold snap has caused sea, lake, river and beach temperatures to drop a few degrees in what many wild swimmers believe is the mid-teens Celsius sweet spot. Energizing enough to get the buzz but not too cold to freeze you to the bone afterwards.
“Have you heard of the Pareto principle?” asks Dr. Mark Harper, anesthetist, researcher and author of Chill out: the cold water swim cure. “Here, 80% of the results are achieved with 20% of the effort. So we are now in that nice time where when the temperature is between 15 and 20°C you are probably getting 80% of the benefits of cold water for just 20% of the effort.”
Wild swimming was already on the rise, but the Covid pandemic has pushed the number of activities into high gear. Lidos, once unloved and anachronistic, have risen again: Cleveland Pools in Bath, Britain’s oldest outdoor pool, has just reopened after 40 years of neglect and a £9.3million refurbishment. The Outdoor Swimming Society (OSS) had 300 members when it was founded in 2006; now it has 175,000 through its channels and one million visitors annually to its website. The society recently asked its members why they swam outdoors: 94% responded that the main reason was “joy” and said they felt happier and less stressed after a swim.
Such testimonies are, of course, anecdotal, and even the OSS acknowledges that the Society is “a border cult built on enthusiasm.” And that remains a recurring question mark for wild swimming and cold-water diving: Despite all the evangelical claims made by fans, there’s minimal scientific evidence to back them up so far. That’s not to say the benefits don’t exist, just that there haven’t been enough rigorous clinical studies to prove them either way.
That is beginning to change, however, and over the past month academic papers have appeared dense and fast. Harper was part of a team investigating whether ocean swimming could be “a novel intervention for depression and anxiety.” The study enrolled 53 people – 47 women, five men, one non-binary person – in an eight-session swimming class and tracked their well-being via questionnaires. Harper says the mental health of many participants improved significantly, and he’s particularly encouraged by the fact that three months later, 80% were still swimming outdoors and reported finding the activity helpful.
“It’s just a proof of concept, but the numbers are phenomenal,” says Harper. “If you said you got this effect from a drug, people wouldn’t believe you. It’s way better than any effect you get from SSRIs [selective serotonin reuptake inhibitors commonly used to treat depression]for example.”
Harper was also working on a project with NHS frontline workers this year to see if swimming outside could improve symptoms of stress and work-related burnout. Participants swam in a pool in London or in the sea in Cornwall and reported an overall 14.8% improvement in well-being after six weeks.
Before you plunge into the nearest lake, however, words of warning were heard British Journal of Sports Medicine. There, Mike Tipton, professor of human and applied physiology and a global expert on extreme environments, points out that HM Coastguard deployments related to open water swimming increased by 52% between 2018 and 2021. There was also a 79% increase in deaths – from 34 to 61 in the UK.
Tipton was encouraged to publish the newspaper after watching the BBC reality series Freeze the Fear with Wim Hof about the Dutch extreme athlete who spent more than three hours in direct full-body contact with ice. “Although there was a safety message in the beginning, when you look at these programs you would tend to step into cold water,” says Tipton. “So we felt it necessary to just say, ‘Look, we’re a tropical animal, and that’s one of the greatest stresses you can put on the body.’ We’re not trying to stop people from doing things; We’re not the fun police. But there are ways to maximize the potential benefits and minimize the risks.”
Here Tipton and Harper are in complete agreement. If you’re considering dipping a toe in the pool, especially this winter, you should get a medical exam first. Start at a spot with lifeguards and gradually get into the water: resist the urge to jump, dive, cannonballs. Spend less than 10 minutes in the water even if you are not cold. From personal experience swimming outdoors, this is a key point: I’ve had dips where I timed it right and felt dizzy all day, and others where I’ve spent too long in the water and my teeth are still there two rattle hours later.
Tipton and Harper also recognize that more research needs to be done before we attribute transformative powers to outdoor swimming. “I can see the anecdotal answers, but what we don’t know about open water swimming is the active ingredient,” says Tipton. “So when you swim in open water, you meet friends, you put yourself in beautiful surroundings, you float, you’re supported by the water, you get some exercise, you get cold, you come out and you have cake.
“There are so many other factors,” Tipton continues, “but we don’t know which ones are actually responsible for the claimed benefits.”