How cold is the water?
Cold shock can occur in waters
below 15.5° C (60° F) (an average water temperature for most Canadian lakes during boating season).
Effects of cold water
Sudden immersion in cold water can have very serious consequences. The physical responses to the sudden change in skin temperature are profound, particularly if a person is not wearing a lifejacket or PFD to keep their head above water.
Wearing a lifejacket also helps the immersion victim conserve body heat by keeping their head out of the water and allowing them to assume a motionless posture with their back to any waves. Flotation devices with thermal protection can lessen the impact of cold shock and significantly improve survival times for those immersed for long periods.
Cold shock (short term response)
The cold shock reflex is a large gasp for air combined with a dramatic increase in blood pressure and heart rate. The ability to hold one's breath is virtually eliminated in a severe uncontrolled hyperventilation that produces intense feelings of panic. Without flotation the inspiration of water and subsequent drowning can occur very quickly.
Swim failure (short/medium term response)
After the first few minutes the effects of swim failure begin to occur. Muscle spasms, weakness, numbness and loss of dexterity can immobilize the best of swimmers and make it very difficult to hold on to a rope or flotation aid. Being able to put on a lifejacket or PFD in these conditions (even if it were luckily floating nearby) is near impossible.
Hypothermia (long term response)
After about 30 minutes of cold water immersion the body core temperature can begin to drop creating the early stage of hypothermia brought on by long term exposure to cold.
Hypothermia is a medical term that describes a serious condition where the body core temperature falls to dangerous levels as a result of exposure to cold. Immersion in cold water results in heat loss by conduction and the rate of loss is affected by several factors including body type, insulation and the temperature of the water.
Hypothermia does not usually begin until after 30 minutes of immersion. It is a long-term effect that can result in unconsciousness and death in a matter of hours depending on the temperature. Often the shorter term effects of coldshock and swim failure result in drowning long before hypothermia has set in if the person is not wearing a lifejacket or PFD.
Click for more information...
• about the research & physiology of cold shock in Essentials of Sea Survival by Golden/Tipton, 2003
• Survival in Cold Waters by C.J. Brooks, 2003 for Transport Canada
Research
• Canadian Red Cross Society Drownings in Canada and other water-related injuries -
10 Years of Research (Published in 2006) Module 1 - Overview (pdf 2.8MB) - Module 2 - Ice & Cold Water (pdf 3.7MB)
• CSBC/SMARTRISK Report 2003 "Will It Float?"
• Brooks C.J., Survival in Cold Waters, Staying Alive Transport Canada, 2003
• Essentials of Sea Survival - Golden/Tipton 2003
• Golden F, Tipton, M. Essentials of Sea Survival Human Kinetics, 2002
• Brooks CJ. Survival in Cold Waters. Ottawa Transport Canada, 2001
• Tipton MJ. The Initial Responses to Cold-Water Immersion in Man. Clinical Science 1989;
77:581-588
• Hayward JS, Hay, C., Matthews, B.R., Overweel, C.H., Radford, D.D. Temperature Effect on the
Human Dive Response in Relation to Cold Water Near-Drowning. Journal of Applied Physiology:
Respiration, Environmental and Exercise Physiology 1984; 56:202-206
• Barcroft H, Edholm, O.G. Temperature and Blood Flow in the Human Forearm. Journal of
Physiology 1946; 104:366-376
• Vincent MJ, Tipton, M.J. The Effects of Cold Immersion and Hand Protection on Grip Strength.
Aviation, Space, and Environmental Medicine 1988; 59:738-741
• Brooks CJ. Survival in Cold Water (presentation), 2003
Cold Water Bootcamp
• Learn more about cold water survival at Cold Water Bootcamp
Thermal protection
Wearing a lifejacket also helps the immersion victim conserve body heat by keeping their head out of the water and allowing them to assume a motionless posture with their back to any waves. Flotation devices with thermal protection can lessen the impact of cold shock and significantly improve survival times for those immersed for long periods.