As one type of diving suit, the drysuit is a garment designed to provide a layer of protection between the skin of the wearer and the surrounding water. Unlike a wetsuit, which allows a small portion of water to collect in the suit, the drysuit effectively seals off all portions of the body that are covered, so that no water can enter the suit. This is accomplished with a form fitting design that includes watertight seals at the wrists, neck, and ankles of the drysuit. Often, these seals are made of latex, which will remain supple for about two years while maintaining the watertight seal.
One of the distinctive attributes of the drysuit is an inflation valve that will allow the wearer to make adjustments in the buoyancy of the suit. This is especially important, as the drysuit is often worn for deep-sea scuba diving. As the diver descends, using the valve to inject gases that have been stored in a diving regulator regulates pressure inside the suit. When the diver is ready to return to the surface, a vent valve on the suit allows the wearer to release the gas from the suit. One some drysuits, the vent valve will work automatically, while on others the wearer will have to operate the valve manually. In the event of a malfunction of the vent valve, it is possible to release the gas during an ascent by slightly loosening the neck or one of the wrist seals.
There are essentially two types of drysuits that are used frequently. The membrane drysuit is usually made of materials such as vulcanized rubber, or a combination of nylon and butyl rubber. Membrane drysuits do not offer any real thermal protection in colder water. However, many divers will wear an undersuit with the membrane suit, which is what actually provides the thermal protection and also retains the gases for buoyancy. In warmer climates, the diver may choose to omit the undersuit, but this will impact the effectiveness of the gas released to create the buoyancy. Membrane drysuits are relatively easy to put on and take off when necessary.
Neoprene drysuits, on the other hand, do provide a degree of thermal insulation as well as help to retain the buoyancy. In general, the neoprene drysuit is often considered the better of the two options, since no undersuit is necessary and the properties of the neoprene make it less susceptible to losing buoyancy in the event that the suit is damaged or breached in some manner. The neoprene drysuit is a much more rigid than the membrane style, and takes more time and effort to put on and take off.
While many types of drysuit come with ankle seals, there are models that include built in foot protection as well. The modern versions of the drysuit also tend to include a zipper that is usually found either down the front of the suit, or across the shoulders. Many divers find the types with the front zipper easier to use, and also more comfortable to wear. Persons who dive professionally often find the neoprene drysuit to be their best bet in warmer waters, while the membrane drysuit is better for situations where the ability to move with some degree of freedom is more important.