Cold swimming has suddenly become one of the most popular pastimes in the UK.
Made famous by ice-bathing Dutch motivational swimmer Wim Hof and taken up en masse by people during the pandemic, enthusiasts are often evangelical about the physical and mental benefits of an icy jump.
However, experts are increasingly concerned that people are taking the plunge without realizing the potentially deadly effects of cold water.
The number of deaths from open water swimming in the UK rose by almost 80 per cent from 34 to 61 between 2018 and 2021.
And the number of emergency calls to the Coast Guard reporting swimmers in distress increased more than 50 percent in 2021, according to a study published in the study British Journal of Sports Medicine earlier this month.
The report’s lead author, Mike Tipton, a professor of human and applied physiology at the University of Portsmouth, is concerned that people are taking up cold-water swimming too quickly.
“As a tropical animal, going into cold water is a really big stress,” he said I. “We are not made for this. We want to be naked in 28°C air, not naked in 10°C water.
“Without wanting to be too nanny-static, it just seems like an area that could use some sort of guidance.”
According to Professor Tipton, people starting out in cold water swimming — whether it’s in open water or in an ice bath in their garage — should treat it like training for a marathon.
This should include a medical check-up and a phased exercise program where people entering the water build their tolerance to cold water.
This is especially important for people who take up the hobby later in life, Prof Tipton pointed out, who may have existing health conditions that make them more susceptible to cold water shock.
Cold water shock can cause people to hyperventilate, causing blood pressure to rise and the heart to work harder. A doctor may look for conditions such as asthma, cardiovascular disease, or high blood pressure that can cause problems with these conditions.
In April this year, Kellie Poole, 39, died after wading into the icy waters of a Derbyshire river in her bathing suit.
It’s not clear what caused Ms Poole’s death, but even young, healthy people can have undiagnosed conditions that can be fatal if suddenly exposed to ice-cold water.
“Just like you would do if you were to start running a marathon gradually, you could have a health check to make sure you didn’t have an underlying problem,” Professor Tipton pointed out.
Starting at the right time of year is also important. Late summer and early autumn are a good time for sea bathing as sea temperatures in the UK peak at around 18°-20°C
Swimmers should then swim regularly, preferably with an experienced group, over the winter as water temperatures gradually drop.
In early spring, a barrage of warm weather can feel like a warm day perfect for a dip. However, this is the most dangerous time to start swimming in cold water as the water temperature can still drop below 10ºC°C – Dangerously cold for inexperienced swimmers.
That’s another reason to never jump in the water or dive without first testing the temperature, Prof Tipton said, as the involuntary gasping from cold shock can prove fatal.
“Cold water shock has a respiratory response where you can’t hold your breath, gasp, hyperventilate,” he explained.
“The first breath you take when you step into cold water is two to three liters. The lethal dose of salt water in the lungs is about 1.5 liters.”