Immersion in cold water can kill in just minutes—the colder the water, the greater the risk. One's swimming ability does not improve one's chances of survival. Research shows that a sudden immersion into cold water (65° (F) or less) starts as a series of incapacitating reflexes that increase the risk of drowning. Many waterbodies in Montana are fed from high mountain springs and don't get above 65° even in the summer making cold water immersion a threat all year long.
Understanding your body's reaction to cold water and the four stages of immersion will increase your ability to respond appropriately.
This response begins immediately upon immersion and will peak within the first 30 seconds to 5 minutes. Breathing changes are immediate and may include an involuntary gasping, rapid breathing, dizziness and confusion, resulting in water inhalation and possible drowning. Circulatory changes include a sudden rise in heart rate and blood pressure, possibly resulting in stroke or heart attack. Wearing a life jacket prior to a fall will greatly reduce the chances of water aspiration.
After being in cold water for 3 to 30 minutes, it becomes increasingly difficult to swim or move. The nerves and muscles in the arms and legs cool quickly because of the constriction in blood flow. Manual dexterity, strength of handgrip and movement speed will drop 60 percent to 80 percent. This limits a person's ability to assist with rescue by catching a rope, put on a life jacket, or climbing a boat ladder.
Someone who survives the first two stages of cold water immersion faces the onset of hypothermia. The continuous loss of body heat eventually decreased the core body temperature and can result in death. A person wearing a life jacket can survive for hours and increases their chance for detection and rescue.
A person is still at risk after they have been rescued. During the process of hypothermia, the vascular system and its ability to move blood is impaired. The body tries to rewarm itself and causes a huge load on the heart. Cold water immersion victims need to be handled very gently and treated by a knowledgeable medical team for transport to a hospital.
Small Craft Advisory (January/Feruary 2008 ) is a publication of the National Association of State Boating Law Administrators featuring articles about cold water immersion.
The Alaska Boating Safety Program produced this video to educate boaters on how to prepare for,
avoid, and survive a cold water immersion event.
Cold Water Boating Video