Respect the Water: Understanding Cold Water Shock and Staying Safe in Open Water

For many, a warm day can create a false sense of security. The air may feel pleasant, but water temperatures can remain dangerously cold, particularly in rivers, reservoirs, lakes and coastal environments. This sudden difference between air and water temperature can trigger a physiological response known as cold water shock – a factor that is often misunderstood and underestimated.

Open water swimming has experienced a surge in popularity in recent years, with many people embracing the physical and mental benefits associated with cold water immersion. However, experienced cold water swimmers and safety advocates are keen to stress that enjoyment of the water must always be accompanied by respect for it.

"Cold water doesn't care how fit you are or how confident a swimmer you are," explains cold water expert Fenwick Ridley. "Every entry into open water deserves respect. The key is understanding what your body is about to experience and giving yourself time to adapt."

What is Cold Water Shock?

Cold water shock is the body's immediate response to entering cold water. Contrary to popular belief, it isn't limited to winter conditions. Water temperatures between 10°C and 15°C are enough to trigger the response, even on warm and sunny days.

The sudden immersion causes cold receptors in the skin to fire rapidly, particularly around the hands, feet and face. This can result in an involuntary gasp reflex, rapid breathing, increased heart rate and a temporary loss of breathing control.

"The shock response is often at its most dangerous in the first minute," explains cold water specialist Gilly McArthur. "People can panic because they feel unable to control their breathing. That's why how you enter the water matters so much."

Enter Slowly, Never Jump

One of the most important safety messages from experienced cold water swimmers is simple: don't jump straight in.

Instead, enter the water gradually, allowing your body time to adapt. Splash water onto your arms, legs and face before submerging your shoulders. The face contains cranial nerve receptors which can help trigger a calming response and reduce heart rate.

"Focus on your breathing," says Ridley. "Take a steady breath in and a longer breath out. The aim is to stay calm and relaxed. If you can control your breathing, you're already reducing the risk."

Even experienced pool swimmers should exercise caution. Open water presents very different challenges, including changing temperatures, currents, tides and reduced visibility.

Building Confidence Safely

Cold water immersion is something that should be approached gradually over time.

Many experienced swimmers recommend starting with short exposures and prioritising adaptation rather than distance or performance. The goal isn't how far or how fast you can swim, but how well you can understand and manage your body's response to the environment.

As McArthur explains: "Your perception changes with experience. The water may still feel cold, but you become better at recognising the sensations and responding appropriately rather than reacting with panic."

If you begin shivering heavily, feel unusually cold, or notice a loss of coordination, it's time to leave the water.

The Part Many People Forget: Getting Out Safely

While much attention is placed on entering cold water, experts say that what happens after a swim can be just as important.

The body's core temperature can continue to fall even after leaving the water, a phenomenon sometimes referred to as "afterdrop". Moving around vigorously or attempting intense exercise immediately afterwards can accelerate heat loss rather than aid recovery.

"Rewarming should be slow and deliberate," says Ridley. "Have warm clothes ready, dry yourself gently, layer up and give your body time to recover. The warming-up process may take longer than the swim itself."

Swimmers are encouraged to prepare before entering the water by having warm layers, a hot drink and snacks ready for afterwards. Adequate energy intake can support the body's natural warming process.

Never Swim Alone

Perhaps the most important safety advice is to avoid entering open water alone.

Swimming groups and local clubs have become an important part of the open water community, providing not only companionship but an additional layer of safety. Having others nearby means help can be summoned quickly if something goes wrong.

Open water conditions can change rapidly, and even experienced swimmers can encounter difficulties.

Respecting the Water

There is no doubt that cold water swimming can offer a range of benefits, from improved wellbeing and connection with nature to a sense of achievement and community. But advocates are keen to emphasise that these benefits come from developing a respectful relationship with the water, not from pushing limits.

The recent tragedies seen across the country are a reminder that water safety education remains vital.

"Cold water swimming can be incredibly rewarding," says McArthur. "But the most important lesson is to respect the water every single time. Conditions change, temperatures change, and our bodies respond differently day to day. Taking a few extra moments to enter carefully and understand the risks can make all the difference."

As more people seek relief from warm weather around rivers, lakes and coastlines, experts hope greater awareness of cold water shock and safe entry practices will help prevent further loss of life and encourage people to enjoy the water safely.

Get the Right Equipment 

Part of what has made cold water swimming so popular is its simplicity. All you need is a wetsuit and a changing robe and you're ready to get going! 

After all, you don’t need too much gear to take the plunge and for the brave-hearted out there, even a wetsuit can be perceived as extreme comfort. Below are a few additional items that can make it a little more enjoyable.

 1. Changing Robe
Unlike towels, which aren’t the best insulators, throwing a Red Equipment waterproof changing robe into the mix is ideal for changing and warming up comfortably without exposing yourself and keeping protected. Red’s all-weather jacket functions not only as a great change robe but can also protect you from the cold and windy elements in any outdoor activity.

2. Swimming Cap
It’s no surprise that adding a swimming cap to your kit bag will prove results when in the water. Not only are they helpful for managing long hair and keeping you warm they are often brightly coloured which will help keep you nice and visible. 

 3. Swimming Tow Float
A brightly coloured tow float is an essential piece of safety equipment for open water swimming, helping improve your visibility so you're easier to spot by other water users. The Red Equipment 2-in-1 Reversible Tow Float Backpack combines a comfortable waterproof backpack with a high-visibility tow float dry bag in one innovative design. It allows you to carry your kit to the water, then reverse it into a tow float with waterproof storage for essentials such as your phone, keys and snacks while you swim, before transforming back into a backpack for the journey home.

4. Bring the Friends
Inviting family and friends along can turn cold water swimming into a social event as much as anything else.

Staying safe on the water starts with knowledge, preparation and making informed decisions before every adventure. Whether you're swimming, dipping or simply enjoying time by the water, respecting the conditions and understanding the risks can make all the difference.

For more open water tips and inspiration, follow Fenwick @fenwickridley and Gilly @gillymcarthur on Instagram.

If you're heading out on a paddleboarding adventure, don't forget to PLOT Your Paddle before you launch. Planning your route, checking the weather and tides, and letting someone know where you're going are simple steps that can help you stay safe on the water. Read our guide to PLOT Your Paddle to learn more before your next SUP adventure.