As temperatures rise during the summer months, many people head to beaches, rivers, lakes and reservoirs to cool down. However, while the weather may feel warm, the water itself can remain dangerously cold.
According to the National Water Safety Forum, 193 people accidentally lost their lives in water-related incidents across the UK in 2024. Surprisingly, most of these incidents did not occur at the coast. Around 61% happened in inland waterways such as rivers, lakes, reservoirs and canals.
Recent periods of warm weather have once again highlighted the risks associated with open water. Understanding what cold water shock is, how it affects the body and how to stay safe could help prevent serious incidents and save lives.
As a first aider, here are some of the things to be aware of if you’re around water this summer and how to help if someone gets into difficulty.
What Is Cold Water Shock?
Cold water shock is the body's immediate response to suddenly entering cold water. It can occur in any open body of water, including rivers, reservoirs, lakes, canals and the sea.
When a person enters cold water unexpectedly, the body can react with an involuntary gasp, followed by rapid breathing, an increased heart rate and a rise in blood pressure. This sudden response can make it difficult to stay calm, control breathing or swim effectively.
In some situations, panic can set in quickly, increasing the risk of drowning. The strain placed on the body can also be particularly dangerous for people with underlying health conditions.
While cold water shock itself is rarely the direct cause of death, the loss of breathing control, panic, exhaustion and inability to stay afloat that can follow sudden immersion are significant factors in many drowning incidents.
Many people assume cold water shock only affects inexperienced swimmers, but it can affect anyone, regardless of age, fitness level or swimming ability.
Why Can Cold Water Shock Happen During a Heatwave?
A common misconception is that warm weather means warm water.
In reality, many open water locations remain significantly colder than the surrounding air temperature. According to the RNLI, water temperatures below 15°C are considered cold enough to affect the body, and many UK rivers, lakes and coastal waters remain below this temperature throughout much of the year.
This means that even on a hot day, entering open water suddenly can trigger cold water shock.
Research has also shown that accidental drowning deaths increase significantly during periods of warm weather, as more people are drawn to open water to cool off. Unfortunately, many underestimate how cold the water can be and how quickly the body can react.
Who Is Most at Risk?
Cold water shock can affect anyone who enters cold water unexpectedly, including:
- Open water swimmers
- Paddleboarders
- Kayakers and canoeists
- Anglers
- Runners attempting to cool down
- Dog walkers entering water to assist a pet
- Children playing near water
- Strong swimmers who may underestimate the risk.
Many water safety organisations highlight that drowning is not limited to inexperienced swimmers. Confidence in the water can sometimes lead people to underestimate environmental risks, particularly during periods of hot weather.
Statistics also show that men account for the majority of accidental drowning incidents in the UK.
How Can You Reduce the Risk?
While no activity around water is completely risk-free, there are practical steps people can take to reduce the likelihood of cold water shock.
Enter the Water Gradually
Entering the water slowly allows your body time to adjust to the temperature and may help reduce the severity of the initial shock response. However, it is important to remember that gradual entry may reduce the impact of cold water shock but does not eliminate the risk entirely.
Avoid Jumping Into Unknown Water
Jumping or diving into open water can increase the risk of both injury and cold water shock. Water depth, hidden objects, strong currents and underwater hazards may not always be visible from the surface.
Never Swim Alone
Whenever possible, swim with others and choose locations where help is available if needed.
Avoid Alcohol Around Water
Alcohol can impair judgement, affect coordination and increase risk-taking behaviour, making water-related incidents more likely.
Wear Appropriate Safety Equipment
For activities such as paddleboarding, kayaking and boating, wearing a suitable buoyancy aid can provide additional protection if you unexpectedly enter the water.
What Should You Do If You Unexpectedly Enter Cold Water?
If you suddenly find yourself in cold water, try not to panic.
The first minute after immersion is often the most dangerous because this is when the body's cold shock response is at its strongest. Rapid breathing can make it difficult to think clearly, and many people instinctively try to swim immediately, which can make the situation worse.
Instead, focus on controlling your breathing and keeping your airway clear. Water safety organisations often refer to the "1-10-1" principle when discussing cold water survival. This guidance highlights that following sudden immersion, you have approximately:
- 1 minute to gain control of your breathing
- 10 minutes of meaningful movement before cold incapacitation begins to affect your ability to swim or stay afloat
- 1 hour before severe hypothermia becomes a significant concern
While these timings can vary between individuals and conditions, the principle reinforces the importance of controlling your breathing first and avoiding panic.
The RNLI's Float to Live campaign encourages people to:
- Tilt your head back with your ears submerged
- Relax and try to control your breathing
- Use your hands to help stay afloat
- Spread your arms and legs
- Wait until breathing has returned to normal before attempting to swim or call for help
Once the initial shock passes, you'll be in a better position to assess your surroundings and take further action.
What Should You Do If Someone Else Gets Into Difficulty?
If you see someone struggling in the water, your instinct as a first aider may be to jump in and help. However, entering the water yourself can place you at risk and may create a second casualty.
Instead:
- Call 999 immediately
- If the incident is at the coast, ask for the Coast Guard
- For inland waterways such as rivers, lakes, reservoirs and canals, follow the call handler's instructions
- Encourage the casualty to float if they can hear you
- Throw something that floats if available
- Direct emergency services to the exact location
Many water safety organisations promote the principle of "Call, Tell, Throw" to help people respond safely without entering the water themselves.
Why First Aid Matters After a Water Rescue
Even after someone has been rescued from the water, they may still require urgent medical attention.
Cold water immersion can affect breathing, body temperature and consciousness. In severe cases, a casualty may stop breathing, which can rapidly lead to cardiac arrest.
If a casualty is unresponsive and not breathing normally following rescue, call 999 immediately, begin CPR and ask someone to retrieve an Automated External Defibrillator (AED) if one is available.
Understanding how to recognise an emergency, call for help and provide first aid can make a significant difference while waiting for emergency services to arrive.
Learning first aid can help people build confidence and develop the skills needed to respond in a wide range of emergencies, including incidents involving water.
If a casualty has been rescued from the water and is unresponsive and not breathing normally, there are some important differences in the approach to CPR, and some additional aspects that you should be aware of as a first aider:
- Check the airway is open and give five initial rescue breaths
- It is common for casualties rescued from water to regurgitate stomach contents. If this occurs, turn them onto their side, clear the airway if necessary and recommence CPR as soon as possible
- If they start breathing, put them in the recovery position
- You may also need to treat them for hypothermia by covering them with warm clothes or blankets. Remove wet clothing if where practical and protect them from further heat loss
Most importantly, anyone who has experienced breathing difficulties, loss of consciousness, significant cold exposure or required resuscitation following a water incident should receive urgent medical assessment, even if they appear to have recovered.
Enjoy Open Water Safely This Summer
Spending time around water can be a great way to enjoy the warmer months, but it is important to understand the risks that may not be immediately visible.
As a first aider, you can:
- Share this advice with friends and family – knowing quick pieces of advice like ‘Call, Tell, Throw’ can make a big difference
- Encourage others to take first aid training – with workplace, eLearning and community training options available, there is something suitable for everyone
- Refresh knowledge by taking a look at and sharing our advice pages, following us on social media or taking Annual Refresher training
Cold water shock can happen to anyone, even on the hottest days of the year. By taking simple precautions, staying aware, and knowing what to do in an emergency, we can all help make open water activities safer this summer.
Useful Resources:
- RNLI Float to Live
- Royal Life Saving Society UK
- St John Ambulance First Aid Training
- St John Ambulance First Aid Advice
Sources:
National Water Safety Forum (Water Incident Database)
