The recreational diver is
chiefly concerned with thermodynamics because these principles dictate
how heat
is lost from the body. There are three ways that heat can be transmitted from the body and into the surrounding environment: conduction, convection, and radiation. The image to the right shows an example of all three mechanisms of transfer. |
 EARTHFORTRESS.com
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| Conduction Conduction is the transmission of heat due to direct contact. For example, if you drop an egg into boiling water, when you remove the egg, it is warm. |
| Convection Convection is the transmission of heat via fluids, in this case, heat from the body via water. Fluids near the body become warm via conduction. As the fluids become warmer, they become less dense and rise away from the body in respect to the surrounding colder fluids, allowing the colder fluids to take their place. |
| Radiation Radiation refers to the transfer of heat via electromagnetic waves. An example of this is the heat the you feel from the sun. While diving, you may feel heat due to radiation if you hold your hand in front of a high intensity underwater light such as those used in film. |
 Diver with early symptoms of
hypothermia
Aqua Views online SCUBA magazine The second
main option for retaining warmth on a dive is a drysuit. A drysuit is
designed to keep the wearer completely dry and surrounding by a layer
of air. This layer acts as an insulator. As no water is touching the
body, a drysuit will keep a diver warmer than a wetsuit.
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Two questions all divers must ask themselves are: 1) Why do I get colder faster in the water than at the surface? 2) How do I keep from getting cold while on a dive? Water is
more dense than air- about 770 times as dense. Because of this, the
water molecules are closer together than air molecules, making water
able to conduct heat about 20 times faster than air.
There are two general options for retaining warmth while on a dive, a drysuit or a wetsuit. A wet suit is made out of material, usually foam neoprene, that traps small bubbles. These bubbles retain air to act as an insulator, reducing conduction. A wetsuit also traps a small layer of water close to the body. After the body heats the water, it is trapped inside the wetsuit and cannot be lost due to convection. This is a reason why proper fitting wetsuits are a must.  Retention of warmth due to a wetsuit eastlancsdivers.com |