Safety tip of the week: cold water shock & hypothermia


Great piece by our member Kate Jenkins about some of the greatest hidden dangers when sailing.

Have you ever sailed without a life jacket, reassuring yourself that you could comfortably keep your head above water in the unlikely event of a man overboard? Unfortunately, being able to swim is no protection against drowning, and a major reason for this is the poorly understood phenomena of cold water shock. Unlike hypothermia, cold water shock occurs immediately, and is likely to be responsible for a far great number of drownings.

Cold Water Shock

Cold water shock is the body’s natural response in the first few seconds after sudden exposure to cold water (usually less than 15 degrees). The sudden cold exposure causes the body to involuntarily gasp. If this happens whilst the person’s face is underwater (for example after falling overboard, or whilst waves are breaking over their face), water will be inhaled into the lungs. In extreme cases, this can result in immediate drowning – irrespective of how strong a swimmer the person is. The initial gasp is followed by further gasping or hyperventilation, increasing the amount of water being swallowed or taken into the lungs. The sensation of not being able to breath naturally creates panic, which in turn further exacerbates hyperventilation and water inhalation. Although this is perhaps easier said than done, the most important thing someone in this situation can do is try and control their breathing and avoid panicking whilst awaiting help.

Cold Incapacitation

After the first minute in the water, a person enters a second phase called ‘cold incapacitation’. The body attempts to preserve heat by constricting blood vessels and redirectly blood flow away from non-essential areas. This results in muscles becoming weak or paralysed, significantly hampering a person’s ability to swim or stay afloat whilst awaiting rescue. Constricting blood vessels also places additional stress on organs including the heart. In people with pre-existing heart disease, this additional stress could cause serious complications such as heart attacks.


If the person remains in the water, they will eventually either drown, or begin to show the effects of hypothermia. Hypothermia is when the body’s core temperature drops below 35 degrees. In early stages it causes shivering and mild confusion. In later stages a person will become increasingly weak and confused (even trying to remove clothing and other warming devices) until the drop in body temperature eventually causes a cardiac arrest. Treatment for mild hypothermia is with removal of wet clothing, warm drinks, and warm blankets/clothing.

It’s important to keep in mind that heat is lost much more quickly in water than in air, and so hypothermia can occur even in warm water (remember that normal body temperature is approximately 37 degrees, and that even ‘warm’ seas are rarely more than 20 degrees).

Avoiding Cold Water Shock… Lifejackets are key!

Wearing an appropriate life jacket will keep a person’s head above water, and prevent drowning from water inhalation or muscle paralysis due to cold water shock. It will also help a person minimise heat loss in water by allowing them to float in the ‘HELP’ position (‘Heat Escape Lessening Posture’: legs crossed and knees raised to chest, arms tightly down at sides, and forearms hugged to chest)

Lifejackets may also prove useful for rescuers when pulling the person out of the water.

Basic First Aid

If you are concerned that someone may be suffering from cold water shock or hypothermia, immediately remove them from the water, including removing any cold/wet clothing and gently warming them with warm drinks and dry clothing. Someone should remain with the person at all times, and if in any doubt, call an ambulance.

In a worst case scenario, if a person is unconscious when pulled from the water, they should be rolled on their side (into the ‘recovery positon’) to encourage water to drain out of their mouth and lungs. Make sure you keep them warm by replacing wet clothing with warm dry blankets/clothing whilst awaiting the arrival of an ambulance. If they are not breathing, leave them on their back and commence CPR immediately.

Remember that cold water shock is an involuntary response, and can affect anyone, irrespective of their sailing experience, swimming ability, or time spent at Mt Buller this ski season. The most important way of protecting yourself and your crew is to always wear a lifejacket, and to practice your man overboard drills regularly. If you are concerned about someone who has been in the water, it is always safest to call an ambulance so that they can be immediately assessed. Make sure you keep them warm and dry whilst waiting for paramedics to arrive.