Immersing yourself in cold water is increasingly popular and is touted to provide many health benefits, but sudden immersion in water less than 15ºC can be very dangerous. ‘Seasoned’ cold water swimmers enjoy repeated visits and as a result, their body acclimatises to cold more readily. For others, though, it is a shockingly cold experience that can – and has – lead to death.

Immersion deaths represent the third most common cause of accidental death in adults, and the second in children, in most countries.

Average seawater temperatures around the UK are just 12ºC, with rivers and lochs not even reaching that. Remember too that when the water temperature warms a little during the summer, the air temperature has probably risen much more – leading to a greater difference between the two than other times of year. Also, consider that deep lochs don’t warm very much at all even in the summer months.

Sudden immersion in cold water can happen for several reasons – through simply falling in or voluntarily entering cold water suddenly – jumping in! Young men and the elderly are cited as the most ‘at risk’ groups, but anyone who enters cold water is potentially at risk.

Cold Shock Response in your body

The sudden change of temperature from immersion in cold water has a profound and varied effect on the human body. The largest organ in the body – your skin – is suddenly immersed in cold water more than 20 degrees lower than your core temperature! Cold Shock Response is the body’s reaction to the sudden drop in skin temperature and greatly increases your risk of drowning.

Cold Shock Response causes a sudden gasp for air, followed by uncontrollable breathing – rapid breathing caused by anxiety or panic. This can cause immediate problems due to inhalation of water into the lungs. Just half a pint of water is enough to overwhelm the lungs and cause an adult to start drowning.

The lungs will be overwhelmed completely with 1.5 litres of seawater. 1.5 litres sounds like a lot of water to drink for example, but when hyperventilating, an adult will inhale that volume or air in a single respiration very easily. It’s easy to imagine how the panicking, hyperventilating casualty in the water could inhale that volume of water.

The impact on blood flow and heart rate.

The sudden cooling of the skin also causes blood vessels to shrink, which in turn makes it harder for blood to flow. At the same time the heart rate increases, which combined with the reduced blood vessel size, leads to an increase in blood pressure. This means that the heart has to suddenly work much harder. The rapid rise in work rate, and increase in blood pressure can thus lead to serious cardiovascular problems and sudden cardiac arrest in some cases.

The other response experienced by some people is ‘the diving response’. This is initiated by the immersion of the face in cold water and causes the holding of breath, and abnormal heart rhythms designed to conserve oxygen in diving mammals. In humans this response often conflicts enormously with the cold shock response, again causing cardiac problems and sudden death in many cases.

What to do if you are immersed in cold water

The advice from the RNLI is to try your best to relax and ‘Float to Live’. 

• Fight the natural urge to thrash about to get out of the situation.

• Concentrate on trying to float on your back to keep your face clear of the water to stop you from panicking. 

• Floating doesn’t work if you struggle, so trying to float encourages you to stay still. 

• Bring your stomach and chest up to the water surface, and tilt your head back a little to keep your airway clear.

• The initial cold shock response will pass in less than a minute, so trying to stay calm and controlling your breathing is the best course of action. 

Once you have regained control, then seek help, swim or paddle on your back to the shore, board or vessel if possible. 

First aid for a casualty with Cold Water Shock:

Once a casualty is removed from the water quickly, they will probably be shivering violently and possibly struggling to use their fingers or hands. Their body will have concentrated all the blood into their core so their fine motor skills will be reduced. The core is the heart, lungs, brain and vital organs in the body and is the body’s priority in times of trauma at the expense of blood supply to the other limbs.

Their core temperature will drop dangerously if they have been in the water for a longer period.  The exact length of time will vary between casualties. Core cooling in most people will occur only after several minutes – that’s not a long time -so swift action and care for the casualty is imperative.

• Help them get to shelter, ideally out of the wind. 

• Remove wet clothing and give them warm dry clothes to wear. 

• Give them warm fluids to drink and food to eat.  Food is fuel and helps because their body will generate heat if it has fuel to burn. 

• Reassure and monitor them and get medical help if they do not warm up or improve.

First Aid for Drowning

Drowning is when your lungs are overwhelmed by water and the heart and brain are deprived of life-giving oxygen. Drowning does not always lead to death but can lead to life-changing illness or injury due to having impaired airways over some time.

Combined with the potential of cold water response, it is crucial to identify and immediately deal with a drowning person.

Drowning is not like in the movies – someone who is drowning will not be able to shout, wave or splash about. They will be still and quiet and struggling to use their limbs. If someone IS shouting or waving, they WILL probably need help before things get worse for them.

In summary, when dealing with a person who has drowned, you should:

1. Get them out of the water, onto their back and give them FIVE rescue breaths

2. Do 1 minute of CPR with 30 chest compressions to 2 rescue breaths

3. Then, if they do not come around, phone EMS/112 immediately and tell them where you are

4. Continue to do CPR until the ambulance arrives

5. If they do come around, reassure and monitor them for 24hrs. If they have any difficulty breathing, are extremely tired or have a behaviour change, get them to hospital as this may be a sign of ‘secondary drowning’.

What is “secondary drowning”?

Secondary drowning is not a medical term but refers to your body’s response to a near-drowning episode and can occur up to 48 hours after the incident. It is rare but should be considered when dealing with a casualty who has had an episode involving water.

It can be caused by any near drowning incident if someone has had water get into their lungs. Swallowing even a small amount of water into your lungs is serious. Children have been known to have died up to 24 hours after getting water into their system.

There are three important signs that you should look out for:

• Difficulty breathing,

• Extreme tiredness

• Changes in behaviour.

• Persistent cough

• Chest pains

• Vomiting

• Difficulty speaking

Monitoring a casualty for a few days after an episode in the water is important and they should be taken to hospital if any of the symptoms appear.