Hypothermia develops when the body loses heat faster than it can produce it, causing core body temperature to fall below 35°C (95°F). For surfers, kitesurfers, windsurfers, swimmers and other water users, prolonged exposure to cold water, wind and wet equipment can create a serious risk even when conditions do not appear extreme.
Cold-water safety is not only about hypothermia. Sudden immersion can trigger cold water shock almost immediately, while continued exposure can reduce muscle function and coordination before significant hypothermia develops. Understanding these different stages can help you recognise danger earlier.
This guide explains the signs of hypothermia, how it differs from cold water shock, how to reduce the risk and what first aid measures can be taken while professional medical help is arranged.
What Is Hypothermia?
Hypothermia occurs when the body's core temperature falls below 35°C (95°F). It is a medical emergency that requires appropriate medical attention.
The body normally regulates its internal temperature by balancing heat production and heat loss. Cold water, wet clothing, wind and prolonged exposure can disrupt that balance and cause core temperature to fall.
As cooling progresses, physical and mental function can deteriorate. Severe hypothermia can affect consciousness, breathing and circulation.
Can You Get Hypothermia in Mild Water Temperatures?
Yes. Hypothermia is not limited to freezing water.
Prolonged exposure to cool water can gradually lower body temperature even when the water is well above freezing. How quickly this happens varies considerably between people and situations.
Factors affecting cold exposure include:
- Water temperature.
- Time spent in the water.
- Wind and weather conditions.
- Activity level.
- Body size and individual physiology.
- Thermal protection.
- Fatigue and physical condition.
- Exposure after leaving the water.
Do not use air temperature alone to judge whether a session presents a cold-water risk. Warm weather can coexist with water cold enough to create serious problems.
Cold Water Shock vs Hypothermia
Cold water shock and hypothermia are different responses to cold exposure.
Cold water shock can begin almost immediately after sudden immersion in cold water. It can cause involuntary gasping, rapid breathing and major changes in heart rate and blood pressure. These reactions can make it difficult to control your breathing and increase the risk of drowning.
Hypothermia develops later as the body continues losing heat and core temperature falls below 35°C.
Between those stages, continued cooling can also reduce muscle strength, dexterity and coordination, affecting the ability to swim or hold onto equipment.
This means someone can become seriously impaired by cold water before they meet the definition of hypothermia. For more detail on the immediate response to sudden immersion, see our guide to cold water shock.
Why Cold Water Is Dangerous for Watersports
Cold water can remove body heat rapidly, particularly during prolonged immersion.
For watersports participants, the risk is influenced by more than water temperature alone. Wind exposure, session length, fatigue and the condition and suitability of your thermal protection all matter.
The period immediately after leaving the water also matters. Wet equipment combined with wind can continue cooling the body until wet layers are removed and the person is dried, sheltered and insulated.
Early Signs of Hypothermia
Recognising excessive cooling early gives you an opportunity to leave the water before the situation becomes more serious.
Possible warning signs include:
- Persistent shivering.
- Feeling unusually cold.
- Numbness.
- Reduced hand dexterity.
- Difficulty operating equipment.
- Fatigue.
- Reduced concentration.
- Increasing clumsiness or poor coordination.
During watersports, reduced hand function can be particularly important. Difficulty gripping a boom, controlling a kite, operating a release system or handling other equipment may indicate that cold exposure is already affecting performance.
Do not wait for severe symptoms before ending a session.
Signs of More Serious Hypothermia
As body temperature continues to fall, neurological and physical function can deteriorate further.
Warning signs can include:
- Increasing confusion.
- Slurred speech.
- Poor coordination.
- Marked drowsiness.
- Unusual or irrational behaviour.
- Reduced responsiveness.
- Shivering that becomes less effective or stops as the condition becomes severe.
- Slow or abnormal breathing.
- Loss of consciousness.
Hypothermia is a medical emergency. If you think someone is hypothermic, contact the local emergency services and follow professional instructions.
Do Not Rely on Shivering Alone
Shivering is an important response to cooling, but it should not be your only indicator of severity.
Someone who is cold and shivering may still be able to communicate normally, while worsening hypothermia can lead to confusion, impaired coordination and reduced consciousness.
In more severe hypothermia, shivering may eventually decrease or stop. The absence of shivering therefore does not mean the person is becoming warmer.
How to Prevent Hypothermia During Watersports
Prevention begins before you enter the water. Match your thermal protection and session plan to the water temperature, air temperature, wind and expected duration of exposure.
- Check water and weather conditions before your session.
- Use thermal protection appropriate for the activity and conditions.
- Add a hood, gloves or boots when conditions require them.
- Make sure your wetsuit fits correctly and remains in good condition.
- Avoid extending a session once cold begins affecting concentration or physical control.
- Know where you can exit the water safely.
- Bring dry, insulating clothing for immediately after the session.
- Consider how wind exposure will affect you once you leave the water.
What you wear depends on the activity and conditions. For activity-specific preparation, see our guides to what to wear for surfing and what to wear for kitesurfing.
A wetsuit can only provide useful thermal protection when it fits and functions properly. Our guide to wetsuit care explains how cleaning, drying and storage can help maintain the condition of your equipment.
Know When to End Your Session
Do not treat persistent shivering, numb hands or deteriorating coordination as something you simply need to tolerate.
Cold can affect the exact abilities you need to return to shore safely. A kitesurfer may struggle with control systems, a windsurfer may lose grip and balance, and a surfer or swimmer may lose paddling or swimming efficiency.
Leave enough physical capacity to exit the water before cold exposure becomes a serious problem.
First Aid for Suspected Hypothermia
If you think someone has hypothermia, contact the local emergency services and follow their instructions. While waiting for professional help, the priority is to prevent further heat loss and move the person away from continued cold exposure as safely as possible.
- Move the person indoors or to a sheltered location as quickly and safely as possible.
- Protect them from wind and cold ground.
- Remove wet clothing and replace it with dry clothing or insulation when this can be done safely.
- Wrap the person in dry blankets, towels, a sleeping bag or other insulating material.
- Keep the head covered.
- Handle someone with significant hypothermia gently.
- Stay with the person and monitor their responsiveness and breathing.
- Follow the instructions given by emergency medical services.
Do not use a hot bath, hot water bottle or heat lamp to rapidly warm someone with suspected hypothermia, and do not rub or massage their arms, legs, hands or feet.
Can You Give Someone With Hypothermia a Warm Drink?
If the person is fully awake and able to swallow safely, current NHS first aid guidance allows a warm non-alcoholic drink and some sugary food while medical help is being arranged.
Do not give food or drink to someone who is confused, very drowsy, vomiting, losing consciousness or otherwise unable to swallow safely.
Do not give alcohol. Alcohol does not safely treat hypothermia and can interfere with the body's response to cold.
How Should You Rewarm Someone?
Preventing further heat loss is the immediate priority while professional medical help is arranged.
Move the person somewhere sheltered, remove wet clothing when this can be done safely and replace it with dry clothing and insulation. Blankets, dry towels, sleeping bags and protection from wind and cold surfaces can help conserve body heat.
Avoid aggressive attempts to rapidly heat someone with suspected hypothermia. Do not use a hot bath, hot water bottle or heat lamp, and do not rub or massage cold arms, legs, hands or feet.
Using an Insulated Hypothermia Wrap
Professional and specialist rescue systems may use insulated wraps or hypothermia cocoons to reduce continued heat loss.
These systems can help provide insulation from wind, moisture and cold surfaces while professional help is arranged.
Follow the instructions supplied with the specific rescue equipment and the directions of trained rescue or medical personnel.
What If the Person Becomes Unresponsive?
An unresponsive person with suspected hypothermia requires immediate emergency medical assistance.
Check whether the person is breathing normally and follow the instructions of the emergency dispatcher.
If the person is not breathing normally, begin resuscitation according to current first aid guidance and the instructions of emergency services.
If cold exposure followed a drowning incident, our drowning first aid and CPR guide explains the emergency response to drowning.
Common Hypothermia Mistakes
- Assuming warm air means the water presents no cold-exposure risk.
- Confusing cold water shock with hypothermia.
- Staying in the water despite persistent shivering or declining physical control.
- Ignoring loss of hand function or coordination.
- Failing to prepare dry clothing for after the session.
- Rubbing or massaging someone with suspected hypothermia.
- Trying to rapidly rewarm someone with a hot bath, hot water bottle or heat lamp.
- Giving alcohol as a method of warming someone.
- Giving food or drink to someone who cannot swallow safely.
- Delaying emergency medical help when hypothermia is suspected.
Frequently Asked Questions
What temperature is considered hypothermia?
Hypothermia is defined as a core body temperature below 35°C (95°F). In a coastal or watersports emergency, however, you may not be able to measure core temperature accurately. If the circumstances and symptoms suggest hypothermia, seek professional medical help.
Can you get hypothermia while surfing in summer?
Yes. Water can remain cold even when the air temperature is warm. A long session combined with inadequate thermal protection, wind and fatigue can lead to excessive cooling.
What are the early warning signs of excessive cooling?
Persistent shivering, numbness, reduced hand function, fatigue, poor concentration and declining coordination can indicate that cold exposure is affecting you. Symptoms vary, so do not wait for every sign to appear before leaving the water.
What is the difference between cold water shock and hypothermia?
Cold water shock is an immediate physiological response to sudden immersion in cold water and can disrupt breathing and cardiovascular function. Hypothermia develops later as core body temperature falls below 35°C. See our full guide to cold water shock for more detail on the immediate immersion response.
Can someone become impaired before they are hypothermic?
Yes. Continued cold-water exposure can reduce muscle strength, dexterity and coordination before core temperature falls below the threshold used to define hypothermia. This can make swimming, paddling or operating watersports equipment increasingly difficult.
Should you rub someone who has hypothermia?
No. Do not rub or massage someone with suspected hypothermia. Protect them from further heat loss, handle them gently and seek professional medical help.
When should you call emergency services for hypothermia?
Hypothermia is a medical emergency. If you think someone is hypothermic, contact the local emergency services and follow their instructions. Signs such as confusion, slurred speech, poor coordination, marked drowsiness, reduced responsiveness, abnormal breathing or unconsciousness indicate a particularly serious situation.
Final Thoughts
Cold-water safety starts before hypothermia develops. Sudden immersion can cause cold water shock, continued cooling can reduce strength and coordination, and prolonged exposure can eventually lower core body temperature enough to cause hypothermia.
For watersports participants, prepare for the water temperature and conditions rather than judging cold exposure from air temperature alone. Use appropriate thermal protection, monitor how the cold is affecting you and leave the water before declining dexterity, coordination or concentration compromises your ability to return safely.
If you think someone has become hypothermic, treat the situation seriously. Prevent further heat loss, move them to shelter where possible, insulate them and contact professional medical services.
Disclaimer
This article provides general educational information and does not replace professional medical advice, accredited first aid training or instructions from emergency services. First aid guidance can vary between countries and may change over time. In an emergency, contact your local emergency services and follow the instructions of qualified professionals.