Wetsuits

Heat loss in water ( read as a class)

If you've ever noticed that you feel perfectly comfortable walking around at 20 degrees Celsius, but water of the same temperature feels pretty cold quickly, it's because water is a much better conductor of heat than air. So on land, the roughly 17 degree difference between air temperature and your body temperature is no big deal. However, when diving, the water that comes in contact with your body warms up, expands, and quickly carries the heat away from you. As a result, you feel cold in no time. In fact, water removes heat from your body between 25 and 40 times faster than air!

Another reason for greater heat loss when diving is breathing. Breathing generally accounts for about a quarter of our body's heat loss in the form of exhaled warm air. The deeper we dive, the denser the air we inhale. At a depth of 10 mteres the air we breathe in and exhale is already twice as dense as on the surface, which means that the heat loss from exhaling is twice as large as well.

This accelerated heat loss is why divers wear "exposure suits," diving suits that are either sealed dry suits that do not allow any water in, or wetsuits where some water gets in. Dry suits work by using a thin layer of air in addition to the insulating properties of the suit. In wetsuits, a thin layer of water that's been warmed up by your body does the same. Unfortunately, underwater physics throw divers another curve: the increasing pressure compresses the insulating gas bubbles inside the exposure suit, making it ever less effective the deeper you go. That's why there are recommendations as to what type and thickness of suit you should wear at different water temperatures.