Into the danger zone

Looks are deceiving, water's cold

Cold water kills. After a swimmer has gone through cold shock and swimming failure, hypothermia sets in. After an extended time in the water the swimmer will lapse into unconsciousness, resulting in either drowning or cardiac arrest.

The longer a body is in the water the more heat it will lose. Heat is lost from surface tissue to the water. As surface tissue cools heat begins to transfer from deeper in the body to surface tissue.

The rate of heat loss from convection and conduction is affected by three factors:

• Temperature difference between the body and water; the bigger the difference the faster the heat loss will be.
• Surface area exposed; heat is transferred faster when more warm surface area exposed to the cold water, that is, whether the swimmer is partially or completely immersed.
• Relative movement of water next to the body. Moving around brings more cold water into contact.

Other factors that impact heat loss are:

• Clothing that acts as insulation.
• Ratio of body mass to surface area, for example, a taller thin person of the same body weight as a shorter person will lose heat faster.
• Subcutaneous fat, essentially insulation.
• Whether the individual ate beforehand and what they ate.
  

Dress for the water temperature is an expression all kayakers are familiar with. I've seen numerous posts to our kayak newsgroup about advice on dressing to paddle in the cold. There's no one pat answer because of personal differences in body composition. Also, some people are more suseptible to cold than others.

My advice is to experiment with a clothing combination that works specifically for you, keeping in mind the above info. And, dress for the maximum amount of time you could be in the water; that will depend on your paddling group and whether you practiced self and assisted rescues.