A drysuit is waterproof suit worn by SCUBA divers to provide exposure protection while in the water (other water sports also have drysuits but they are much simpler than those used for SCUBA). While there are many types of drysuits available, they all have several features in common: they all have various water tight seals over the openings, have valves for allowing compressed air into the suit and alowing the air to escape and they all have waterproof zippers.

Most drysuits have neck and wrist seals. A few suits have ankle seals while others use attached boots or socks. Some suits do away with the wrist seals in favor of dry gloves which usually snap into place using some sort of locking mechanism.

The drysuit seals are made up of either latex or neoprene. Many divers find the neoprene to be more comfortable but they tend to allow water to leak into the suit. Latex seals are the most common type. Regardless of the type of seal, they must be replaced after a few years.

The drysuit itself can be made up of any number of materials but they generally come in two types, shell suits and neoprene suits.

Shell suits are typically made from a trilaminate (butyl rubber laminated on both sides by nylon), a bilaminate (butyl rubber and nylon), Cordura, vulcanized rubber or DUI's CF200 fabric (a patented material made by Diving Unlimited International).

All shell suits have several features in common:

  • The material does not compress under pressure

  • The material provides little or no insulation

The laminates offer the advantages of being quick drying, light and easy to repair but are the more fragile of the various materials. Vulcanized rubber is also quick drying and easy to repair but is quite heavy. It is often used in polluted waters by commercial divers. Cordura is a heavier material but quite tough. CF200 is also quite heavy and slow drying but is possibly the most durable.

As shell suits don't offer any thermal protection, undergarments must be worn under them. Popular materials are usually quick drying, pull moisture away from the skin and provide insulation even when wet. Thinsulate and Polartec fleece are the most common materials. By changing the undergarments worn, the shell suit diver can adjust the thermal protection as needed.

Shell suits are usually baggy as the most common materials don't stretch. The CF200 material is a notable exception.

Neoprene suits are made of either foam neoprene (the same material as wetsuits) or compressed neoprene]. These suits are designed to provide some insulation but compress at depth. They are stretchable so they allow a closer fit than most shell suits.

The compressed neoprene suits are designed to be somewhat compression resistant but do not have the inherent insulation of the foam neoprene suits and are usually worn with undergarments. The fact that these suits are compressible means that the diver's buoyancy characteristics change with depth (the suit becomes denser) forcing the diver to dive overweighted (if he is five pounds negative at the surface, he may be 11 pounds negative at 90 feet). When the suit compresses, it also loses its insulating properties. The main advantages of the neoprene suits is that if they were to flood, the diver will still have some insulation from the material itself. This is less of an issue with today's synthetic fabrics that do a good job of keeping a diver warm even when completely soaked. The other advantage of the neoprene suits is usually cost.

The other difference between the various drysuit models is zipper location. Since dry zippers are very expensive (the most expensive component of the suit besides the suit itself), using the shortest length that will allow the diver to don/doff the suit will reduce the overall cost. The location favored for placing shorter zippers is across the shoulder on the back of the suit. To don these shoulder-entry suits, the diver steps in through the zipper, places his arms in the suit and then pulls the remainder over his head. His dive buddy then needs to zip him up. The other location for the dry zipper is diagonally across the chest from the shoulder to the hip. These suits allow the diver to zip himself up but since the zipper is quite a bit longer, they cost significantly more than than a comparable shoulder-entry suit.

Besides zipper location, there are many other drysuit options.

Many manufacturers offer two types of boots. The integrated boot option involves a sole being attached to the bottom of the suit. The disadvantage here is that the suit itself gets the wear and tear of simply walking around on the beach/boat/rocks/etc. The other option is a soft sock sewn onto the suit that is worn inside a non-integrated boot. These boots often look quite like hiking boots. Of course, a diver may find himself having left his boots at home and not be able to dive (fins designed for boots are unwearable without boots).

Another popular option for male divers is a overboard dump valve aka pee valve. This is a tube that is attached to a condom catheter that leads to the outside of the suit allowing a diver to urinate during longer dives. This is considered an essential piece of equipment for divers doing decompression dives (women divers are forced to wear dipers).

The other options include things like pockets, suspenders, knee, butt and elbow pads and the list goes on. Buying a drysuit can be like buying a car and is often the most expensive piece of equipment a diver will purchase (and diving is a very expensive sport).