What Is a Drysuit and How Do They Work?

Serious cold water diving is not for everyone. Most divers complete their certification course in a wetsuit and continue to dive wet even in cooler waters. However, for divers wishing to continue their hobby year-round or expand the range of their dives to colder waters, a drysuit is the only way to go.

Drysuits are well worth the price and the minimal time required to learn to use them properly. For anyone who dives frequently in water temperatures below 60 degrees Fahrenheit, using a drysuit will tremendously increase the enjoyment of your dives, lengthen your dive season, and prevent an otherwise negatively cold outlook towards local diving.

In this series, we will cover the basics of dry suit function, look into a variety of suit materials and optional features, review dry suit care and maintenance, and consider the versatility of drysuits and how they can become a vital piece of gear as your diving expands.  

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The Purpose of Exposure Protection

An diver wearing a drysuit dives under ice

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Water conducts heat away from the body twenty times faster than air. As a result, divers must wear adequate exposure protection in the form of a wetsuit or drysuit to prevent discomfort and (in extreme cases) hypothermia. A wetsuit keeps a diver warm by limiting water circulation through the suit. In combination with an insulating layer of neoprene, this allows the diver's body to heat up the trapped water and keep the diver warm. However, for long dives, very cold waters, or very deep dives, a wetsuit may not be sufficient.

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What Exactly Is a Drysuit?

An ice diver uses a drysuit to explore the White Sea in Russia

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A drysuit is a waterproof suit that seals an layer of air between the diver and the water. A combination of water tight zippers and neck/wrist seals make drysuits (relatively) easy to don and doff. Because air conducts heat away from a diver more slowly than water, a diver who stays dry underwater will not lose body heat as quickly as a wetsuit diver. Air, however, is not particularly insulating on its own, so most drysuit divers add insulating undergarments to keep them warm in cooler waters.   

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Inflating and Deflating Drysuits

A diver poses wearing a drysuit

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The first time you dive in properly fitted drysuit, you will be surprised at how comfortable you feel floating through the water in a lovely cushion of air. However, the fact that the diver is surrounded by air brings up additional considerations for drysuit users that wetsuit divers do not have to worry about.

It's important to monitor and adjust the volume of the air inside a drysuit during a dive. Just like the air in a diver's other body spaces and BCD, the air in a diver's drysuit is compressible. As a diver descends, the air in his suit will compress and diver will end up shrink-wrapped if he doesn't offset the compression. During ascent, a diver must release the expanding air from his suit to avoid an uncontrolled ascent.

Drysuits are inflated using a power-inflation valve. The disk-shaped valve is normally located on the diver's chest, and is connected to the regulator first stage by a low pressure inflator hose (similar to the hose connected to a BCD's power inflator). The diver simply presses down on the valve to add air to his drysuit.

Drysuits have a second valve for deflation, typically located on the left shoulder. A diver operates the deflation valve by positioning his body with the valve at the highest point and then pressing down on the valve to open it. Most modern deflation valves may also used with the valve twisted open so that a properly trimmed diver can deflate hands-free by simply raising his shoulder – putting the valve at a higher point where excess gas will naturally want to escape.  

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Drysuit Undergarments

A diver wearing a drysuit investigates cold water coral formations

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Drysuit undergarments insulate a diver from the cold water. Unlike a neoprene wetsuit, which compresses as a diver descends, drysuit undergarments provide consistent warmth as they do not compress. This is a huge benefit on cold or deep dives, as the diver has the same level of insulation regardless of his depth. Choosing an appropriate undergarment for your dive is key, and will depend on the temperature of the water. Many drysuit divers own multiple undergarments for different environments. These range from thin, moisture-wicking base layers to full body suits of fleece, down, or synthetic materials. Some undergarments are quite thick, so keep this in mind when sizing your suit. Note that drysuits can be used with dry gloves, under which divers have, the option to wear insulating wool gloves to keep their hands warm and dry.

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Necessary Qualifications

Technical divers using drysuits underwater

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Contrary to popular belief, student divers can complete their open water check out dives in a drysuit provided they have first completed a confined water drysuit orientation with their instructor. Whether you are a novice or an experienced diver, be sure to practice with a drysuit for the first time in confined water under the guidance of an instructor. It's a good idea to take a drysuit orientation course; doing so will get you comfortable in the suit faster than if you try to learn on your own.  

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Dive Cold Water Without the Chill

Ice Diving
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Once you learn to use a drysuit properly, the number of dive sites you can visit and the diversity of experiences you can have underwater will increase. There's a huge difference between diving in cold water and being cold on a dive. With proper thermal protection and techniques, a diver should never be too cold underwater.