Cold-Water Immersion (CWI) and Hypothermia

Cold-water immersion (CWI) kills. Knowing how the body reacts to CWI can prepare boaters to correctly respond to this life-threatening situation and improve the chances of survival.


Phase Time Period Reaction
Cold Shock First few minutes of immersion The shock of CWI can cause sudden water inhalation and drowning due to involuntary gasping, hyperventilation , panic, and vertigo. Sudden changes in blood pressure, heart rate, and heart rhythm can also result in death.
Swim Failure Three to 30 minutes following immersion The muscles and nerves of the arms and legs cool quickly. Motor control (manual dexterity, grip strength, and speed of movement) can all drop drastically. Even physically fit boaters can lose the motor control necessary to pull themselves out of the water or even to keep their head above the surface. Death occurs by drowning.


Immersion Hypothermia After 30 minutes (depending on water temperature, clothing, body type, and behavior in the water). Hypothermia occurs when your core body temperature drops below its normal range, eventually leading to unconsciousness, and death, with or without drowning.
Post-Immersion Collapse Occurs during or after rescue. Once rescued, there is still danger from collapse of arterial blood pressure leading to cardiac arrest. Inhaled water can damage the lungs, and heart problems can develop as cold blood from arms and legs is released into the body core.

Prepare for cold-water conditions by always dressing for the water temperature and wearing appropriate floatation. Wear a float coat, survival suit, or wet suit (long or short) during cold weather. Always prepare for CWI when the combined water and air temperature is less than 110 degrees Fahrenheit.

A boaterís chances of surviving a CWI depends on sufficient flotation for keeping an airway, controlling breathing, heat retention and timely rescue by self or others. If multiple persons end up in the water, attempt to stay together, and "huddle" to limit heat loss. Treat victims of cold water immersion by replacing wet clothing with dry materials (blankets, coats, clothing, etc.), talk to them, and immediately seek medical attention.


Donít Panic Protect your airway, and get to the surface as quickly as possible. Control breathing. Hold onto something or stay still. Focus on floating with your head above water until the cold shock response lessens.
Get Out of the Water Try to reboard the boat, even if it is swamped or capsized. Get as much of yourself out of the water as possible. The rate of heat loss will be slower out of the water than if immersed in water. If you cannot reenter the boat, put on a life jacket. If no life jacket is available, grab anything that will help you float .
Slow Heat Loss Keep head and neck out of water. In as little as 10 minutes, you may become unable to self-rescue. Minimize movement. Donít take your clothes off unless absolutely necessary. Staying with the boat is often a better choice than swimming. If you must swim, swim on back, arms tight to sides of torso, thighs together, knees bent, flutter kick with lower legs
Signal Rescuers Use a portable air horn, whistle or visual distress signals if available. Continue signaling by all available means.

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