Wetsuits slow heat loss underwater by trapping a thin layer of water against a diver’s body. While the diver still gets wet, his body rapidly heats up the thin layer of water trapped against his body to nearly body temperature. If the suit fits properly, the warm layer of water does not circulate away from the diver’s body. The warm layer of body temperature water conducts less heat away from the diver than the cooler surrounding water, which keeps the diver warmer than he otherwise would be.
Wetsuits are not perfect.
The warm layer of water trapped against a diver’s skin still conducts some heat away from the diver’s body, and it loses some of its warmth through the wetsuit. Given enough time, a diver wearing a wetsuit may still become chilled, depending upon the type of wetsuit. In colder temperatures or on very long dives, a wetsuit may not be sufficient to keep a diver warm.
Consider the following when selecting a wetsuit for a given dive environment:
1. The Tighter the Wetsuit, the Warmer You Will Be:
A wetsuit keeps a diver warm by trapping water inside the suit. A snug suit will more effectively trap and hold water against a diver’s skin than a loose suit. A wetsuit that does not fit snugly will allow cold water to circulate into the suit, which will cause the diver to become chilled more quickly. Tighter is better – up to a point. A suit that is too tight across the chest will restrict a diver’s breathing, which can be uncomfortable and even dangerous.
2. The Thicker the Suit, the Warmer You Will Be:
Underwater, heat is lost through the neoprene layer of a wetsuit. The thicker the wetsuit, the less heat will be lost and the warmer the diver will be. However, thicker wetsuits tend to restrict movement, so divers will be most comfortable choosing the thinnest suit that will keep them warm in the anticipated dive environment.
3. The Deeper You Dive, the Colder You Will Be:
The neoprene rubber in wetsuits is lightweight and flexible because it is manufactured with millions of tiny air bubbles sealed inside the rubber material. Because these air bubbles are completely sealed, the air inside them will expand and compress according to Boyle’s Law. The deeper a diver descends, the more the air bubbles compress and the thinner the wetsuit becomes. Because a thinner wetsuit is less insulating, the deeper a diver goes, the colder he can expect to be.
4. The Longer the Dive, the Colder You Will Be:
While wetsuits do help to slow heat loss underwater, a diver’s body still gradually loses heat over long periods of time. After long dives, a diver may feel chilled from this slow heat loss. Select a thicker suit for longer dives.
5. Natural Insulation:
While a diver’s “natural insulation” is not a characteristic of the wetsuit itself, a diver’s body fat will affect how rapidly he chills underwater. Divers with a low body fat percentage will cool more quickly than divers with a normal percentage of body fat. Divers who have very little body fat may want to consider choosing a thicker suit than average divers diving in a similar dive environment.
6. Short Suits vs Long Suits:
Short wetsuits expose a diver’s lower legs and arms to the water. Short wetsuits still help to keep a diver comfortable in warm water because they cover the diver’s torso. They are not as effective as long suits because more of the diver’s skin is exposed to the water.
A good wetsuit slows heat loss underwater to the point that a diver remains comfortable throughout a dive. Consider characteristics such as wetsuit thickness and fit, as well as the length and depth of the dive when selecting a wetsuit for a given dive environment.