Safety experts estimate that half of all drowning victims actually die from the fatal effects of cold water, or hypothermia, and not from water-filled lungs. This is shown in the sinking of the Titanic after it hit an iceberg. Loss of body heat is one of the greatest hazards to survival when you fall overboard, capsize or jump into the water. Cold water robs the body of heat 25 to 30 times faster than air. When you lose enough body heat to make your temperature subnormal, you become hypothermic.

Sudden immersion in cold water cools your skin and outer tissues very quickly. Within 10 to 15 minutes, your core body temperature (brain, spinal cord, heart and lungs) begins to drop. Your arms and legs become numb and completely useless. You may lose consciousness and drown before your core temperature drops low enough to cause death.Rule of 50

To show the effects of cold water here are two variations of the "rule of 50":

- An average adult has a 50/50 chance of surviving a 50-yard swim in 50 degree F. water.

- A 50-year-old man in 50 degree F. water has a 50/50 chance of surviving for 50 minutes.

How cold is "cold water"?

Cold water does not have to be icy. It just has to be colder than you are for hypothermia. A person who is wet, improperly dressed and intoxicated can become hypothermic in 70-degree water. The rate of body heat loss depends on water temperature, the protective clothing worn, percent body fat and other physical factors, and most importantly what you do in the water. The U.S. Coast Guard defines any water under 70 degrees F. as being "cold water."

Survival time

Different activities in the water consume varying amounts of body heat. The more energy (heat) you expend, the quicker your body temperature drops, reducing your survival time. As shown below, wearing a life jacket, also known as a personal floatation device (PFD), can add hours to your survival time.

For an average adult in 50 degree F. (10 degree C) water:

- Drown-proofing = 1 1/2 hours

- Swimming slowly = 2 hours

- Treading water = 2 hours

- Holding still = 2 3/4 hours

- Huddle = 4 hours

- Wearing a PFD = 7 hours

The drown-proofing method is a warm water survival technique which has the person conserving energy by relaxing in the water and allow the head to submerge between breaths while the person floats. This method is NOT recommended in cold water, since about 50 percent of heat loss is from the head.

Cold water survival

If you suddenly find yourself in the water, don't panic. Calmly follow these procedures to increase your survival time. The single most important thing you should do is minimize body heat loss.

- Do not remove clothing, despite what you may have been told. Instead, button, buckle, zip and tighten collars, cuffs, shoes. Cover your head if possible. A layer of water trapped inside your clothing will be slightly warmed by your body and help insulate you from the colder water, slowing your rate of body heat loss. Put on a PFD if possible.

- Devote all your efforts to getting out of the water. Act quickly before you lose full use of your hands and limbs. Climb onto a boat, raft or anything floating. Right a capsized boat and climb in. Most boats will support you even if full of water. If you can not right a capsized boat, climb on top of the hull. The object is to get as much of yourself out of the water as pos-sible.

- Do not attempt to swim unless it is to reach a nearby boat, another person or a floating object on which you can climb or lean. Unnecessary swimming "pumps" out warmed water between your body and your clothing circulating new cold water to take its place. Unnecessary movement of your arms and legs pumps warm blood to your extremities, where it cools quickly, reducing your survival time by as much as 50 percent.

- If you can't get out of the water try one of the following survival methods:

1. Heat Escape Lessening Position (HELP). Hold knees to chest to protect trunk of body from heat loss. Wrap arms around legs and clasp hands together.

2. Huddle. Huddling together with two or more people will extend survival time 50 percent longer than swimming or treading water.

3. Remain as still as possible, however painful it might be. Intense shivering and severe pain are natural body reflexes in cold water which will not kill you, but heat loss will.