Cold water swimming safety – The risks of winter swimming and how to avoid getting into trouble

Cold water swimming has seen a surge in popularity in recent years. But what are the risks, and what can you do to stay safe during your winter swims?

From avid open water swimmers looking to keep swimming all year round, avoiding the chlorine and lane ropes of the indoor pools at all costs. To those enjoying an invigorating dip in icy waters to experience the wide range of physical and mental health benefits that can come with cold water immersion. More and more people are braving cold water swimming. But it’s important to understand that getting into open water – especially when temperatures plummet – comes with inherent risks.

The good news is there’s plenty you can do to mitigate these risks. We talk you through some essential cold water swimming safety tips, so you can enjoy your time in the water worry-free this winter.

What are the risks of cold water swimming?

With the right gear and a patient approach to getting acclimatised, cold water swimming can be a really great addition to your winter training regime. But to swim safely in cold water, it’s necessary to understand the risks so you can take precautions.

Cold water shock

Cold water shock can happen to any swimmer, regardless of ability. It is the body’s physiological response to sudden immersion in cold water (defined by the Royal National Lifeboat Institution as water under 15 degrees Celsius).

When we plunge into cold water, the sudden temperature change causes the blood vessels closest to the skin to constrict in order to preserve body heat. This sudden constriction in turn raises blood pressure and increases heart rate. This pressure on the cardiovascular system can increase the risk of heart attacks.

Alongside increased blood pressure, cold water shock also triggers the body’s involuntary gasp reflex. Most open water swimmers will have experienced that breathless feeling when you first enter the water at the start of swimming season. This is heightened with cold water swimming, and can cause some swimmers to panic – taking gulps of air, and water, as a result. Even a relatively small amount of water entering the lungs can lead to drowning, which is why cold water shock can be so dangerous.

Cold incapacitation/swim failure

Another risk of swimming in cold water is cold incapacitation. As the body works to keep your core temperature up, it diverts blood away from the limbs and extremities to protect your essential organs from the cold. This means the muscles in your arms and legs aren’t receiving enough oxygen via the blood for proper muscle function to be maintained. As a result, you can start to feel extremely fatigued, with muscle weakness and loss of dexterity. This can cause even experienced swimmers to experience ‘swim failure’ – where the body just physically cannot exert the effort required to keep swimming.

Hypothermia and after drop

Another risk to be aware of if you’re planning to swim for longer periods in cold water is hypothermia.

Hypothermia is defined as when the body’s core temperature drops below 35 degrees Celsius. It can take around 20-30 minutes for hypothermia to set in – after the initial cooling of the skin and the superficial muscle tissues when you first get into the water, the core starts to cool too. Hypothermia can sneak up on swimmers because, unlike cold water shock, it happens gradually.

Alongside the physical symptoms, such as uncontrollable shivering, loss of muscle function, impaired coordination and claw-like hands, which reduce your ability to continue swimming. Hypothermia also has an impact on your mental function, reducing reaction time, making it difficult to speak, and reducing your ability to assess your own condition.

Though not as severe as hypothermia, cold water swimmers can also experience ‘after drop’. They feel fine while they’re swimming, but after exiting the water experience an additional drop in temperature which leads to intense shivering.

Muscle cramps

Cramp is every swimmer’s foe at one time or another. And while the precise cause of cramp is unknown – with hypotheses ranging from muscular fatigue to electrolyte imbalances – anecdotal evidence suggests that cold temperatures can increase the prevalence of muscle cramps.

When we cramp up, the affected muscle goes into an intense, involuntary contraction. Not only is this excruciatingly painful – it’s also dangerous if you’re in the water because it can make it very difficult to swim. If you’re prone to muscle cramps, be aware that cold water may increase the likelihood of experiencing cramp when you’re swimming.

Weather and water conditions

Finally, the physiological impact of cold water on the body aside, the other risk to be aware of is those from your environment. While storms can happen at any time of year, they tend to be more likely during the winter months. This can bring strong wind, which can create dangerously choppy water conditions and strong currents. And heavy rain, which can impact water quality due to sewage overflow and run-off of chemicals and animal manure from agricultural land into rivers.

Therefore it’s important to take the weather forecast and any potential negative effect on water quality into account before you go cold water swimming in open water.

How to swim safely in cold water

Okay, so all those risks might have you thinking that cold water swimming is a terrible idea. But the good news is, now you know the hazards – you can easily take measures to prevent yourself or your swim friends from getting into trouble while you’re cold water swimming. With top tips from high level masters swimmer, Helen Gorman, and Swim England accredited cold water coach and ice swimmer, Fenwick Ridley. Here’s how to keep yourself safe and mitigate the risks of cold water swimming.

Swim with a group and stick to familiar open water swimming locations

It’s always a good idea to swim with others if you’re heading into open water, but even more so during the winter months when cold temperatures elevate the risks. “There are specific cold water swimming courses and workshops that you can take, either online or in person, and there are various coached sessions as well as formal and informal groups that you can join,” says Helen Gorman.

“A coached or group session is obviously the safest environment to swim. If you visit a ‘wild swimming’ location, ideally choose one that you’re already familiar with and ensure that you have at least one buddy with you. A mobile phone with a good signal is essential.”

Make sure everyone in your group knows the signs of cold water shock, swim failure and hypothermia so you can all look out for each other. You can also consider getting the benefits of cold water in a more controlled environment by visiting your local lido if they stay open over the winter months.

Build up your time in cold water gradually

Resist the temptation to dive head first into cold water swimming. Your body will gradually acclimatise, allowing you to swim in colder temperatures with less discomfort. But this adaptation takes time.

Ice swimmer Fenwick Ridley recommends starting your cold water swimming early in the winter season before temperatures drop too low, so you’ve got time to adapt gradually as the water gets colder. “It’s about a staged introduction, doing very little each time.”

MYTH BUSTER: IT’S TIME TO DITCH THE 1 MINUTE PER CELSIUS RULE

It’s common to see open water swimmers referring to the 1 minute for 1 Celsius rule when it comes to how long you can stay in cold water. The idea is that the temperature of the water determines how many minutes you can spend in it. For example if the water temperature was 8 degrees Celsius, some would suggest you could spend 8 minutes in the water. However this ‘rule’ isn’t correct, and it’s a myth Fenwick Ridley is keen to debunk.

“Not everybody is the same – levels of hydration, sleep, general health and stress all vary. You need to look for your own signals.”

Each individual will have different levels of tolerance to the cold, and you might find what’s comfortable one day isn’t the next. Pay attention to how you feel, stay alert for signs of hypothermia and stick within your own comfort zone.

Reduce your time in the water and intensity of your swimming as temperatures drop

Even experienced open water swimmers can be caught out by cold incapacitation/swim failure. Understand that the colder the water temperature gets, the faster your body will fatigue because it’s having to work harder to keep your core temperature up. And because muscle function reduces as the body gets cold. Check the water temperature before you get in, and adjust your session accordingly. Use the pool for your long and/or high intensity swims over the winter and enjoy the tranquillity of an outdoor dip without putting yourself at risk.

Get the right cold water swimming gear and equipment

If you’re new to cold water swimming, don’t feel like you have to swim without a wetsuit right away, or ever. There are some hardy souls out there who can hop into freezing cold water without a shred of neoprene, and not so much as shiver. But if you’re not one of them, that’s okay. Wearing a wetsuit will help to keep you warmer – especially if you treat yourself to a thermal one – and it’ll give you some extra buoyancy which is ideal from a safety perspective.

Keep your extremities comfortable by making use of neoprene swimming gloves and booties. If you’re just dipping, wear a brightly coloured bobble hat to keep your head warm. And if you’re going to put your head under the water, consider wearing a neoprene swim cap to keep the brain freeze at bay. It’s best to wear a brightly coloured swim cap over the top to help keep you visible in the water. Use a tow float with a dry bag too, it’ll further help with visibility. It also gives you something to lean on if you need a rest (though it shouldn’t be relied on as a lifesaving flotation device). And you can use it to keep things like a safety whistle (to attract attention if you get into trouble) to hand.

A changing robe is a great addition to your kit bag so you can warm up quickly after a cold swim. [Photo: WhiteWater Robes]

You’ll also want to have plenty of warm layers of clothing for after your swim. Make sure they’re easy to put on with damp skin and numb hands. And for a real swim hack – have a flask of hot chocolate waiting for you. Trust us, you’ll appreciate it.

RELATED: Essential cold water swimming gear guide

Check weather conditions and water conditions before you swim

Finally, check the weather forecast before you swim. Avoid swimming in high winds, and during or soon after heavy rain fall – the water quality might be compromised which may cause sickness. In the UK, you can make use of apps such as Safer Seas and Rivers Service (SSRS) for real-time alerts on sewage discharge and pollution risks. If you’re planning to swim in the sea/ocean, check the local tide times so you don’t get caught out by a rapidly changing tide. And make sure you take note of any warning flags on beaches. If in doubt – don’t swim.

Knowing the risks and how to mitigate them will help you to enjoy the many benefits of swimming in cold water. If you’re ready to dip your toe in, check out our cold water swimming gear guide to help you get started.