Cold Water Shock: Causes, Symptoms, Treatment and Prevention

Boating in Canada often takes place in very cold water. A maneuvering error, a collision or rough weather can easily cause you to fall overboard, or cause your boat to capsize. When this occurs, there is a high risk of cold water shock. According to the Lifesaving Society, approximately 150 people die as a result of cold-water immersion each year in Canada.

In this article, the National Boating Safety School explains the causes and symptoms of cold shock, how to treat it and what you can do to prevent it from happening in the first place.

What is cold water shock?

Cold water shock occurs when a person is suddenly immersed in cool water. It is an involuntary physical response that can lead to a rapid increase in heart rate and blood pressure, muscle spasms, and difficulty breathing. These symptoms in turn lead to a loss of swimming ability, unconsciousness, and therefore death by drowning.

Cold water shock can be fatal in minutes, even for people who are in good health.

How cold does the water have to be to cause cold water shock?

Despite popular belief, it is possible to experience cold water shock even in waters that are not technically ‘cold’. Water that is 21°C or cooler poses the greatest risk, and since most of Canada’s waters remain at a temperature of 15°C or even colder for most of the year, it’s easy to see that cold water shock is a serious issue for Canadian boaters.

Falling overboard can lead to cold water shock

When boating, cold water shock most often occurs as a result of falling overboard, and not after jumping in the water deliberately or participating in water sports. There are many situations that can cause someone to fall overboard, including failing to follow the Canadian Collision Regulations. Always remember that it is impossible to predict every outcome while boating, and there are many circumstances that can lead to a person’s falling into the water, including rough water, steering issues, and reckless behavior. This is why wearing an approved life jacket or PFD is an extremely important element of safe boating.

Symptoms of cold shock

Cold shock occurs when your body temperature drops suddenly. The most common cause of cold shock is sudden immersion in cold water, when it is called cold water shock. Hypothermia may follow if the person continues to be exposed to low temperatures, particularly if their clothing is wet.

The symptoms of cold shock can be divided into three stages:

Stage one: initial response

The instant the person is submerged, they gasp for breath involuntarily, which can lead them to inhale water if their mouth is below the surface. This is followed by a sharp, fourfold increase in lung ventilation, leading to intense hyperventilation. The person may be unable to speak or call for help, and may suffer small muscle spasms that result in an inability to swim, increasing the risk of drowning.

Additionally, there is a significant surge in heart rate and blood pressure, which can be life-threatening in and of itself, particularly for older or less healthy individuals. These reactions typically last for the first two to three minutes, a critical period following a fall overboard.

What to do: Focus on not panicking and getting control of your breathing.

Stage two: the next half hour

During the intermediate stage, heart rate and blood pressure decrease, as does breathing. Movement and coordination become more and more difficult. The victim becomes confused, irrational and drowsy.

In this phase, occurring between three and thirty minutes after immersion, most fatalities are linked with an inability to swim. In fact, swimming failure leading to drowning is the most common cause of death as a result of cold water shock.

Remember that being a strong swimmer in warm water does not guarantee that a person will be able to swim effectively in cold water or when suffering from cold water shock, due to the intense stress their body is suffering at that moment. Respiratory and cardiovascular responses can interfere with swimming ability, in addition to the so-called  “diving response,” which causes difficulty breathing (apnea), a drop in heart rate (bradycardia), and even cardiac arrest (asystole). It is common to see a person fall overboard and begin to swim, then to witness them go under for no apparent reason during this stage.

What to do: Hold still and float.

Swimming or treading water significantly increases heat loss and can reduce survival time by over 50%.

Stage three: long-term immersion or hypothermia

Cold water does not affect the body the same way that cold air does. When in water, unlike air, the surface area available for heat exchange with the environment comes close to 100%, which is the reason why cold water is so dangerous. In addition, water has a specific heat 1,000 times greater than air and a thermal conductivity about 25 times that of air. Therefore, when the body is submerged in water below its normal temperature (37°C), it will inevitably cool to hypothermic levels.

During the last stage, breathing and pulse are weak, irregular or absent. The victim is usually unconscious. After thirty minutes or more in the water, death may result from hypothermia.

What to do: Get the person out of the water and focus on warming them up in an appropriate manner.

Meanwhile, call for help.

How to treat cold water shock

When experiencing cold shock or hypothermia, the first and most important step is to get out of the cold. If a person falls into cold water, try to get them back onto the boat with the help of a buoyant heaving line if possible. If this is impossible, they should hold onto a buoy or marker, or get to shore before they lose too much body heat or lose their ability to swim. Once they person is out of the water, get them indoors or seek shelter on the boat, because the effects of the wind on wet clothing can aggravate symptoms further.

Next, to the person need to be warmed up. Because their body is in shock, it’s important to proceed gradually. Follow these steps:

1. Remove wet clothes and replace them with dry ones.
2. Cover yourself with dry blankets.
3. Use a hat and scarf to cover the head and neck.
4. Seek contact with dry, warm surfaces that are close to normal body temperature (between 35 °C and 45 °C).

Note: It’s important to be familiar with boating distress signals so that you can call for help in the event of an emergency. Taking a certified course about the rules and risks of boating to get your boating license is vital in order to stay safe on the water.

How to prevent cold shock

There are several steps you can take to prevent cold water shock from occurring. The most important is to take every precaution against falling overboard. For adults, this includes maintaining three points of contact at all times. Staying sober is also important, as many boating accidents are linked with the consumption of alcohol. Staying seated while a boat is underway, being cautious when taking turns, and avoiding boating on rough water or in bad weather are other important steps to consider.

For children, adult supervision is always necessary while on a boat. Help children to stay calm and teach them hold on to railings, in addition to making sure to stay seated while the boat is underway.

Wear a lifejacket or PFD with appropriate buoyancy rating at all times while boating. If you fall into the water, a properly fitting life jacket with a head support will keep you afloat and could save your from drowning, even if you are unconscious or unable to swim.  The thermal qualities of life jacket material will also help you retain your body heat, protecting you to some degree from cold water shock and hypothermia.

Learn about boating safety and get your boating license

Cold water shock can happen to anyone.. The water does not even have to be very cold to trigger this potentially deadly reaction. The best way to prevent cold shock is to be aware of the risks and prepare accordingly.

When boating, it’s important to know the safety measures that can save your life in the event of an emergency. The National Boating Safety School offers an online course that prepares boaters across the country to take our Transport Canada-approved online boating exam. Learn about safe boating practices and get your official Pleasure Craft Operator Card today!