Diving stops being enjoyable if you get chilled under water. If one is not properly prepared heat loss can lead to a serious health threat. Water conducts heat away from your body about 20 times faster than air does, meaning that for a given temperature, water has a greater cooling effect. Even seemingly warm 86ºF water can become chilly after a while.

The loss of body heat can quickly lead to a serious health condition unless you use insulations to reduce the heat loss. Insulation through the use of exposure suits is recommended for diving in water 75ºF or colder. In addition to providing warmth, exposure suits also serve to protect from minor scraps, stings and abrasions.

There are three different types of exposure suits, the body suit, the wet suit and the dry suit.

Body Suit	Usually made form Lycra or nylon. Provide full length abrasion protection, but only minimal insulation. Best suited for tropical water.
Wet Suit	Most common form of exposure suit. Wide variety of thicknesses suitable for insulation in water as cold as 50ºF to as warm as 86ºF.
Dry Suit	Provide insulation by keeping you dry. The warmest exposure suit protection especially in water colder then 50ºF.

The exposure suit you select will depend entirely on the environment you intend to be diving in. The most important considerations are warmth, fit and comfort.

Keep in mind that your need for exposure protection includes your head, hands and feet as well as the rest of your body. This protection is provided through exposure suit accessories - namely hoods, gloves and boots. There are many varieties to choose from, pick according to your diving conditions.

This information was obtained from the Padi Open Water Diver Manual