Cold water danger

Press, 14 November 1977, Page 12

Cold water danger

Cold waters can kill you in two ways — they can drown you or they can slowly chill you to death. If you have an accident while boating or fishing and are washed overboard or have to abandon your boat, your first concern will be to stay afloat. If you are properly prepared, your problem will be solved as a life jacket will keep you buoyant. Otherwise, you will have to tread water or find some buoyant object to cling to. Unfortunately, keeping your head above water will not guarantee your survival until you are rescued — you may have another battle to fight — against hypothermia (deep chilling). Hypothermia is defined as the general lowering of the body temperature. The human body normally maintains a steady 37deg C. If for some reason this temperature is raised or lowered by 6 degrees it is often enough to kill a person.

It is not known how many people die in New Zealand waters from hypothermia, but an average man or woman cannot expect to survive much more than three hours in the sea around the South Island and would only survive seven hours in waters around the North Island. This of course varies considerably from summer to winter, but sea temperatures below 17deg C. will cool the body below the safety temperature. The greatest danger areas are in the cold currents off the southern part of the South Island and in the lakes which are fed by icy mountain streams, where temperatures can reach as low as six degrees Celsius in winter. The main danger, how-' ever, is that most people are unaware of how to prevent hypothermia and

generally do the exact opposite of what thev should do.

The ordinary person can minimise heat loss by as much as two-thirds by putting on clothes rather than removing them before entering the water; gloves, hat, and other clothing help trap a slightly warmer layer of water between the person and the ocean, and so heighten the chance of survival. This of course conflicts with the popular belief that people should take off their clothing so as not to be hampered by it in the water.

Another popular misconception is that when in cold water people should swim or move vigorously so as to keep the limbs warm. While exercise can keep a person warm on land, movement in the water quickens the cooling process of the body. The body has its own natural insulative technique which involves the virtual shutdown of circulation to the surface tissues and the extremities like arms and legs.

This allows the skin to act rather like a wet suit between the warm inner areas of the body and the cold water. If the arms and legs are moved vigorously the blood circulation is forced through the ex? tremities and is cooled. As the blood returns to the main part of the body, it cools the main organs, such as the heart.

Swimming can be recommended only when land is definitely within reach. If you are waiting for rescue keep as still as possible in order to minimise muscular work. Heat will still be produced by the muscles by shivering, but this seems to have less effect on the cirulation than swimming.

Swimming is a more practical method of survival in warm water (17deg C. above). Of course, if your boat is still floating it is important to stay with it to aid rescue sightings.