Updated: May 14
Often, when we discuss cold water immersion in our marine safety workshops, students will bring up the dangers of hypothermia. Their concerns are often misplaced.
It's not exactly that they are wrong. Hypothermia is a killer. But, the body's response to sudden immersion in cold water can kill you long before you develop hypothermia. It's gratifying then, to see the the BoatU.S. Foundation has published a concise article on cold water immersion, Gasp! The Four Stages of Cold Water Immersion, that describes what happens when you fall into cold water, what to do, and what not to do. From the article:
Cold Shock - Falling into cold water provokes an immediate gasp reflex. If your head is under water, you'd inhale water instead of air and it is unlikely you'll resurface if you're not wearing a life jacket. Initial shock can cause panic, hyperventilation, and increase heart rate leading to a heart-attack. This stage lasts 3-5 minutes and at this point you should concentrate on staying afloat with your head above water.
Swimming Failure - In just 3 -30 minutes, the body will experience swimming failure. Due to loss of muscle coordination, swimming becomes a struggle and the body tends to go more vertical in the water making any forward movement increasingly difficult. That's why it is not recommended to swim for help, but remain with the boat or something else that floats while keeping your head above water while awaiting rescue.
Hypothermia - True hypothermia sets in after about 30 minutes. Most victims never make it to this stage since 75% of individuals succumb and die in the earlier stages of cold water immersion. At this stage, regardless of your body type, size, insulation of clothing, acclimatization and other factors, your body's core temperature gets dangerously low. Your survival chances are greatly lessened at this stage. Victims are usually rendered unconscious in this stage.
Post Rescue Collapse - A rescued victim must be handled very carefully. When a person is removed from cold water, the body will react to the surrounding air and the body position. Blood pressure often drops, inhaled water can damage the lungs, and heart problems can develop as cold blood from the extremities is released into the body core. Proper medical attention is essential to re-warm the body safely.
A couple of thoughts: The U.S. Coast Guard defines cold water as water 59° F or colder. That's because research in the 1970's led the Coast Guard to determine that "[A] person of average body build, in good health, wearing work clothes and a life preserver could be expected to survive about eight hours."
That means that cold water shock isn't just a problem at high latitudes. According to today's (December 29) NOAA ocean temperature maps, if you are operating your boat in coastal waters, north of Jacksonville, FL on the Atlantic Coast or north of Cape Conception on the Pacific Coast, your are probably sailing in "cold water". In fact much of the coastal waters of the Gulf of Mexico are currently reported to be below 60° F. In most of the United States, if you fall into the water during the winter months, you are at risk for cold-water shock.
And, did you notice the part about the importance of wearing a life jacket? Since we don't usually plan to fall overboard, capsize, or otherwise get off the boat, there isn't always time to don a PFD before entering the water. In fact, the Coast Guard figures that without a PFD a person is "safe" in 60º F water for about two hours and that 50 percent of us will drown after 4.5 hours. That news should encourage boaters even in so-called "warm water" to wear a PFD on deck.
Anyway, read the whole article, especially for the do's and don'ts of cold water immersion. What you do after you enter the water or after you rescue a victim can have big impact on a victim's chances of survival.
Would you like to learn how to prepare for emergencies at sea and get some hands-on training with survival techniques and gear? Check out our home page for a marine safety workshop near you!