How to adapt to cold-water swimming and extend your open-water swimming season into winter

Want to keep open-water swimming throughout the winter? Here's Professor Greg Whyte with key advice so you can stay safe

How to adapt to cold water swimming and extend your open water swimming season

Extending your open-water season and swimming through the colder months has multiple benefits (more on that later), but the stumbling block for many is that cold water can be unpleasant at best – and dangerous at worst.


So we went to one of the UK’s leading brains in everything sporty, Professor Greg Whyte. This is the man who coached Little Britain’s David Walliams to swim the Channel, after all, so I’m thinking he’ll have no problem advising us triathletes on how to swim relatively modest distances in chilly lakes….

How much does your physiology affect your ability to cope with the cold water?

“To some extent, human physiology’s homogenous,” Greg explains. “We’re pretty  much all the same, but with two key differences. One is your somatotype (body type) as fat makes a big difference, particularly the insulating subcutaneous fat that sits beneath the skin. Mass to body surface area ratio is important, too.

So if you’re quite short, squat and spherical, you’ll cope with cold water more naturally because you’ve got a high body mass to body surface area ratio.”

Greg has bad news for me, though (despite my lockdown relationship with Mr Kipling): “You’re not the body shape that would make a classic open-water cold swimmer because you’re too thin,” Greg says.

“So that makes it much tougher, plus you’re quite tall. What that means is that you’re almost like a radiator – you dissipate heat rapidly. So you’ve got a lot of surface area, but not a huge amount of mass.

“Putting a little bit of extra weight on to give a little bit of insulation with excessive cold open water is a positive thing, so I absolutely wouldn’t be looking to strip weight now!”

How can you prepare for winter open-water swimming?

So unless I want to really hit the snacks hard (and I’m not keen, as that won’t help my running or cycling much), what else can be done to acclimatise before the colder months?

“A key factor is exposure and experience,” says Greg. “People who are constantly exposed to cold environments cope a little bit better because they have much better ‘thermal comfort’. So they don’t feel the cold as much because they’re constantly exposed to it.”

This concept of ‘thermal comfort’ is the only real adaptation we have available to us as humans, so I’m keen to make the most of this in the last of the warmer months. For me, this means starting to swim regularly without my wetsuit, so it’s less of a shock when the colder months come.

Channel swimmers are famously big fans of cold showers, too, and Greg agrees that this can be helpful, but the bad news? Hot showers and baths are off the menu, as I’d just be undoing all my good work.

“You have receptors in the skin, ‘nociceptors’, which measure temperature. What you’re trying to do is desensitise those so they get used to the cold. And the problem is, if you expose them to heat on a regular basis, they just don’t desensitise.”

What kit do I need for cold-water swimming?

As well as acclimatising, getting the right kit can help hugely, too. 

“To swim open water you don’t have to do it in skins,” says Greg, “and I think if you really are uncomfortable swimming in skins, then swim in your wetsuit. It’s not a macho thing. Fundamentally, the most important thing is to enjoy it.

“You can always start off in full wetsuit, balaclava, gloves and booties and, as you acclimatise, reduce the amount of kit you use!

“The first thing I’d recommend is a neoprene cap, as a lot of heat is lost through the head, then adding a neoprene vest under your wetsuit can increase body temperature by 2°C,” adds Greg.

“Crucially, your wetsuit must fit correctly and not allow water to flush through it. Gloves and booties are an interesting one, as once the feet and hands go numb then to some extent that’s not a problem – it’s afterwards as the blood starts to flow back into them that can be painful, so gloves and boots may help. Again, that’s a very personal thing.”

How to keep warm swimming in cold water

It’s time to swim, but there are a couple of things you can do to help yourself cope first. Not getting into the water already cold is key, so we shed our warm layers at the last possible moment.

Greg also advises against cold-water swimming when you’re sleep-deprived, run-down or recovering from tough training or illness, as your body will be less able to withstand the cold.

Once knee-deep, we splash ourselves with water, making sure we wet the face, neck and shoulders. Similar to big races such as Norseman where they spray you with cold water before you get into the swim, this helps you acclimatise and suppresses the dangerous cold-water shock response that can leave you gasping as you enter the water.

Once that’s done, the trick then is to start steadily swimming immediately (no faffing!) as you’ll then start to generate heat from the movement.

After a couple of hundred metres, we pause and Greg gives me some advice on technique. Seems when you enter cold water and start swimming, the temptation is to quicken and shorten your stroke as your body and brain go ‘waaaaah!’, whereas focusing on lengthening at the front of the stroke and extending your body while breathing in a more controlled way will help to calm and relax you, as well as preserving energy.

Secondly, a focus on lengthening also counteracts the body’s natural response to cold, which is to curl into a foetal position to conserve warmth. Bending over at the hips like that will just lead to sinky legs!

The main thing when swimming in open water, though – and especially cold open water – is to stay safe. “First and foremost respect the water – it’s a dangerous environment,” says Greg.

“Submersion in cold water is the leading cause of death in sport and, being 25 times more conductive than air, really strips heat from the body very quickly,” he adds. “Forget the macho approach that we see from many athletes to ‘push through’.

“Also never swim alone – you should always have someone with you.”

How long should you can stay in cold water?

“It’s about experience,” says Greg. “You should progressively increase the period of time exposure. So don’t think to yourself the first time out ‘I’m definitely going to hang in for an hour and a half’, because that’s lunacy.

The first time, you swim for 10 minutes. And if everything’s fine, next time you can do 15 minutes and just gradually increase the exposure time. We’re all different and so people will cope differently with temperatures.”

So how am I doing? “I think you’re coping well with the cold today,” says Greg. “It’s 15°C in the water today, which is pretty cold when you consider that swimming pools are around 28°C-plus and in them you’re ‘thermo-neutral’, which means you’re not really losing heat.

“But this is September – and we’ve got to get through the December and January swims when it gets really cold! Once it edges closer to 10°C and below, that’s when you’ll really start to feel it. But don’t become overconfident, that’s the key!”

How should I warm up after cold-water swimming?

With our swim done, it’s out of the water and on to one of the most crucial elements of open-water swimming in the cold – the ability to warm up again afterwards.

“The most dangerous time for cold open-water swimming is when you get out of the water and we see the ‘afterdrop’, a precipitous fall in core body temperature as blood moves back out from the core to the limbs.

“It’s that classic thing where when you’re swimming, it’s fine — but as soon as you get out, you start to shiver,” says Greg.

“Make sure you’ve got the right equipment to rewarm and do that very aggressively. Don’t stand around in the cold chin-wagging; make sure you’ve got everything to hand and get into a routine which can then enable you to rewarm appropriately as soon as you get out.

“There’s an awful lot of planning about it – it’s not a chance event. You don’t all of a sudden get better at cold open-water swimming. You’ve got to plan how to get better.”

In my colder swims so far this year I’ve been practising just this. My winter kit list will include a woolly hat pulled on over the swim cap while I get dressed, then a towelling robe to dry off with a bigger DryRobe over the top. You can even get post-swim onesies that are easy to pull on and zip up as a baselayer.

Think about how you’ll get dressed with cold hands, too. Mittens with pre-activated heat pads popped inside are a good tip someone shared with me, plus little tricks like wrapping your clothes around a hot water bottle can help.

Also, focus on getting your core warm and dressed first, as your lower body is less important. Have a Thermos flask of your favourite warm drink ready to sip as this’ll help gradually warm you up – and don’t be tempted to jump into a hot bath or shower, as this’ll only encourage the blood to move more quickly to the extremities, exacerbating the afterdrop.

If all this sounds like a lot of effort for what could only be 10-15 minutes of swimming, it’s important to remember this isn’t a heavy training session like a long run or a turbo beasting.

What are the benefits of cold-water swimming?

Think of the ‘soft’ benefits such as improved mental health (the effects of cold swimming on anxiety and depression are well-documented) and the opportunity to be in nature as the seasons change.

For many of us, it’ll be a new challenge and one that’ll mean we need to reign in our inner alpha-triathlete and learn a new skill.

“For triathletes, from a technical and tactical perspective, it’s important to keep swimming open water all year,” advises Greg. “Triathletes always go to the first race of the year and say, ‘My god, the water’s freezing!’ when it’s actually 18°C.

“Whereas if you’ve been swimming in 5°C water throughout the winter, that temperature feels manageable and means you can focus on the swim instead of focusing on the temperature. So keep swimming through the winter. Definitely.”

A winter challenge and the chance to be a better triathlete come 2021? Count me in. You’d just better have the hot chocolate ready for afterwards….