If you fall overboard into cold water, what can you do to extend survival time?

Hypothermia is a very serious condition in which the temperature of the body core drops to below 35 degrees Celsius. This cooling, if not checked, can lead to disorientation, unconsciousness and death. (More about hypothermia)

Prior to the 1960s, the popular wisdom was that drowning was the cause of death in cases where people were lost overboard, especially in temperate latitudes. However, in the 1960s and 1970s attention began to shift to hypothermia as a major cause of death in instances of cold water immersion. 

Since cold water will carry heat away from the body 25 times faster than air of the same temperature, the average body cools rapidly, and within 20 to 30 minutes, depending on water temperature, body core temperature drops to below 35 degrees C (95 degrees F.) An individual's response to cold water will vary from the average depending on a number of factors including clothing, amount of body fat, activity, etc. but the steady decline in core temperature will continue until the person is removed from the water. 

One can extend survival time by simply elevating a portion of the body out of the water onto floating wreckage. Every square inch of body surface removed from the water will incrementally extend the cooling time, even though the air feels cool and a wind may be blowing. 

The brutal facts are these: Without a life jacket, you’ll be lucky to survive 10 minutes in cold water. With a life jacket, you can survive for more than an hour before hypothermia sets in.

After 10 minutes in cold water (59 F or below) your body loses the ability to move. That means you lose the ability to swim back to the boat or even tread water. But contrary to myth, hypothermia doesn’t set in for a while, so if you’re wearing a life jacket, you have time to prepare to survive, according to the National Water Safety Congress’ Cold Water Boot Camp USA (www.coldwaterbootcampusa.org).

“Cold shock can be quite distressing and disorienting,” says Rear Adm. Alan M. Steinman (Ret.), a public health doctor, former Coast Guard director of health and safety, and one of the nation’s foremost experts on cold-weather medicine.

Steinman says you should have your PFD on and adjusted when you’re on the boat because if you hit the water, you will go into cold shock for a minute or two, and it will be very difficult to don the life jacket. “Wearing the PFD could prove decisive to survival in a sudden cold-water immersion if the survivor inhales water during the cold-shock period,” he says.

A sudden gasp is a cold-shock reflex, and if the head is submerged at that moment, the victim can drown. A PFD reduces the odds of the head going under.

Responding to new medical findings and anticipating more ship traffic in the polar regions as snow cover and ice pack melt because of global warming, the International Maritime Organization has updated its “Guide for Cold Water Survival.” The guide stresses that knowing what to expect when you hit the water and being prepared to respond heighten your chances of survival.

“It is most important to realize that you are not helpless to affect your own survival in cold water,” the guide reads. “Understanding your body’s response and simple self-help techniques can extend your survival time, particularly if you wear a life jacket.”

First rule: Don’t go in the water if you don’t have to. “You should try to enter survival or rescue craft directly, without entering the water,” the guide says. There are good reasons for this. The initial responses to cold water are inability to hold your breath and an involuntary gasp, followed by uncontrollable breathing (hyperventilation) and stress on the heart. The colder the water, the stronger these responses. They last one to three minutes, then ease. The key in this phase is not to panic, Steinman says in a 2008 presentation, “Hypothermia, Drowning and Cold Water Survival,” to passenger-vessel safety specialists. Keep your head out of the water so you don’t gulp water in an involuntary gasp and drown. Keep calm so you don’t hyperventilate and faint, which also can lead to drowning.

“If you experience [these cold-shock] responses, you should stay still for the first few minutes of immersion, doing as little as possible until you have regained control of your breathing,” the IMO guide advises.

“Once the cold-shock responses have abated, reducing heat loss is the next major goal,” Steinman says. He says that if you can’t get back to the boat, a life raft or shore in five to 15 minutes, you have to move on to preparing to survive until help arrives before the cold immobilizes you. “Widen the window of opportunity for rescue,” he says.

If you can, get as much of your body out of the water as possible. Climb on the overturned boat or some other floating object. “The less body surface exposed to cold water, the slower the cooling rate of the body and the longer the survival time, no matter what the weather conditions are,” he says. Heat loss from wind chill doesn’t hold a candle to heat loss from immersion in cold water.

If you can’t get out of the water, even partially, minimize movement to limit heat loss. “One of the body’s responses to cold-water immersion is to reduce blood flow to the skin and superficial muscles of the body so as to preserve the amount of heat in the interior vital organs,” Steinman says. “By swimming or thrashing about in the water, the survivor forces relatively warm blood from the core of the body to move to the more superficial muscles of the arms and legs so as to provide those muscles oxygen. This increases the heat loss from the body to the water.”

Curling up in a fetal position (legs pulled up, ankles crossed, arms crossed over chest) minimizes heat loss. This requires a PFD, but some PFDs aren’t stable in a full fetal position. In that case, keep the arms close to the sides of the body and flex the hips as much as possible in a semifetal position, so long as the PFD keeps the head out of the water.

If you’re not wearing a PFD, slowly dog-paddle enough to maintain airway freeboard. Under no circumstances perform drown-proofing — floating in an upright attitude with the face submerged and lifting the mouth and nose above the surface as necessary to take a breath, Steinman says. In cold water, drown-proofing will dramatically increase heat loss. If there are others in the water with you, huddle together with your arms around each other to conserve heat.

The IMO guide notes that it is helpful to wear protective clothing, which traps air and slows the rate of heat loss. It also notes that essential survival action that requires grip strength or manual dexterity — such as adjusting your clothing or life jacket, or locating a life jacket whistle or turning on a light — should be taken as soon as possible after the cold-water shock because your limbs will quickly lose their mobility.

“Settling in for the long haul using the above techniques should occur after the survivor has fully assessed the situation and taken every step to preserve airway freeboard, minimize body heat loss, activate signaling devices and/or call for assistance,” Steinman says.

Once you’re settled in to wait for a rescue, your body temperature will fall at a rate that depends on many factors, including the clothes you wear (a full immersion suit, float coats and pants, layers of clothing and head covering are good insulators); your physique (bigger people with more fat lose heat more slowly); and how much you thrash about in the water (don’t swim, keep still), the IMO guide says.

“In cold water, you may experience violent and distressing shivering and numbness,” the IMO says. “There are natural body responses that are not dangerous. You do, however, need to take action as quickly as possible before you lose full use of your hands.”

Rough water can be a “major detriment” to survival, Steinman says. “Rough water requires the survivor to expend energy to maintain airway freeboard,” he says. It also increases the flushing of cold water through clothing, increasing heat loss; reduces the effectiveness of signal devices; and reduces the survivor’s visibility to rescuers.

The IMO also notes that a significant percentage of people die just before they are rescued, during their rescue or just afterward because of the way they are rescued, because they relaxed too soon or (if they didn’t have a life jacket on) because they suddenly lost buoyancy when they started waving to rescuers to get their attention.

The guide advises staying still in the water and blowing a whistle or shouting to draw attention. The rescue should be done appropriately, preferably with the body in a horizontal or near horizontal position to prevent cardiac arrest.

Lastly, the guide exhorts survivors to maintain a positive attitude about survival and rescue, and fight for that survival even as they are being pulled from the water because if they relax too soon they may just slip under before rescuers can get them aboard.

“Survival is possible, even after many hours in cold water,” the guide says. And your odds improve if you are mentally prepared and know what to expect.

See related article:

- How the body responds

April 2013 issue