Boating Basics Online - Basic Boating Safety Course
Chapter 8 - Accidents and Emergencies

Cold Water Immersion and Hypothermia

Even when the weather is warm, do not forget that in many areas the water can be very, very cold. A sudden unexpected wake or other "unbalancing event" can land you in the frigid water.

Your body can cool down 25 times faster in cold water than in cold air.

What happens when you fall into cold water?

The effects of cold water on the body happen in four stages.

Stage 1 - Cold shock

A sudden, unexpected entry into cold water may cause a reflexive "gasp" (cold shock) allowing water to enter the lungs. Drowning can be almost instantaneous. When you realize you’re about to fall into the water, cover your face with your hands. Covering your mouth is an attempt to avoid gulping water into your lungs.

Stage 2 - Swimming failure effects include:

Stage 3 - Hypothermia

Hypothermia is a condition that exists when the body’s temperature drops below ninety-five degrees. This can be caused by exposure to water or air. The loss of body heat results in loss of dexterity, loss of consciousness, and eventually loss of life.

If you examine the chart below you will see that survival time can be as short as 15 minutes. Water temperature, body size, amount of body fat, and movement in the water all play a part in cold-water survival. Small people cool faster than large people and children cool faster than adults.

PFDs can help you stay alive longer in cold water. You can float without using energy and PFDs cover part of your body, providing some protection from the cold water. When boating in cold water, you should consider using a flotation coat or deck-suit style PFD. They cover more of your body and provide even more protection.

Hypothermia does not only occur in extremely cold water. It can, and does, occur even in the warmer waters of Florida and the Bahamas.

Hypothermia Chart

If the Water
Temp. (F) is:

Exhaustion or

Expected Time
of Survival is:


Under 15 min.

Under 15 - 45 min.

32.5 - 40

15 - 30 min.

30 - 90 min

40 - 50

30 - 60 min.

1 - 3 hours

50 - 60

1 - 2 hours

1 - 6 hours

60 - 70

2 - 7 hours

2 - 40 hours

70 - 80

3 - 12 hours

3 - Indefinite

Over 80



Hypothermia is progressive - the body passes through several stages before an individual lapses into an unconscious state. The extent of a person’s hypothermia can be determined from the following:

  1. Mild Hypothermia - the person feels cold, has violent shivering and slurred speech.
  2. Medium Hypothermia - the person has a certain loss of muscle control, drowsiness, incoherence, stupor and exhaustion.
  3. Severe Hypothermia - the person collapses, may be unconscious and shows signs of respiratory distress and/or cardiac arrest probably leading to death.

The foremost objective for a person in the water is getting control over breathing and getting out of the water. To accomplish this and to limit heat loss, limit body movement. Don't swim unless you can reach a nearby boat or floating object. Swimming lowers your body temperature and even good swimmers can drown in cold water.

If you can pull yourself partially out of the water - do so. The more of your body that is out of the water (on top of an over-turned boat or anything that floats), the less heat you will lose. Especially keep your head out of the water if at all possible - this will lessen heat loss and increase survival time.

The help position.Wearing a PFD in the water is a key to survival. A PFD allows you to float with a minimum of energy expended and allows you to assume the heat escape lessening position -
H. E. L. P.

This position, commonly referred to as the fetal position, permits you to float effortlessly and protect those areas most susceptible to heat loss, including the armpits, sides of the chest, groin, and the back of the knees. If you find yourself in the water with others, you should huddle as a group to help lessen heat loss.

Hypothermia requires medical treatment. If medical treatment is not immediately available, treatment can be accomplished by gradually raising the body temperature back to normal. Re-establishing body temperature can be as simple as sharing a sleeping bag or blanket with another individual, or applying warm moist towels to the individual’s neck, sides of chest and groin. Remove wet clothes as they inhibit heat retention. A warm bath could be used for mild to medium hypothermia, gradually increasing the temperature. Keep arms and legs out of the water and do not attempt to raise the body temperature too quickly.

Do not massage the victim’s arms and legs. Massage will cause the circulatory system to take cold blood from the surface into the body’s core, resulting in further temperature drop. Do not give alcohol, which causes loss of body heat, or coffee and tea which are stimulants (and cause vasodilation) and may have the same effect as massage.

Stage 4 - Post-rescue collapse

The effects on your body after you are pulled from the water can include the following:

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