A drysuit keeps you dry. The waterproof zipper, neck seal, and wrist seals will prevent water from entering inside the drysuit. To stay warm, you need to add layers of undergarments inside the drysuit to keep you warm.
Type of Material
The most common materials used for drysuits are foam neoprene, crushed neoprene, rubber coated fabrics, urethane coated fabrics, and vulcanized rubber. Each material has its own set of characteristics that will affect the performance of the suit. Foam neoprene suits are assembled from sheets of neoprene rubber, the same material used to make wetsuits. Crushed neoprene starts out as a thick sheet of foam neoprene rubber and after the suit is built, it is then crushed resulting in a very thin, yet rugged material. Urethane Coated Fabric drysuits have a urethane tape that is welded to the seams to create a watertight seal. A Trialaminate Suit (TLS) use lightweight layers of tightly woven nylon with a layer of butyl rubber in between. Vulcanized Rubber drysuits are made from a combination of synthetic and natural rubbers which are fused together under heat and pressure creating a one-piece, rubber suit.
Most drysuits will be a back-zip (shoulder-entry) and will have a long zipper on the back of the suit that runs the full length of your shoulders. You will need someone else to zip and unzip your suit for you. Other suits will be front-zip and have the zipper running diagonally along the front of the suit. Many times these suits are referred to as self-entry, however some divers will find they still need a bit of help with the zipper.
Type of Seals
Most common type of wrist and neck seals is latex, however silicone is becoming popular with divers who have skin reactions to latex. Neoprene seals are also available and can provide a softer layer of warmth and comfort against the skin.
The Rockboot style comes with an attached neoprene sock and a detached boot to go over the foot and sock. The Turbo Sole is a flexible, neoprene sock with a solid rubber sole on the bottom of the foot. The Turbo Tech Sole is upgraded to include kevlar material around the toe area for protection from wear and tear. The Rubber style comes with an attached boot that is made of thick rubber.
Care & Maintenance
Like all your scuba diving gear, you need to rinse your drysuit with clean, fresh water inside and outside to rid it of any salt or chlorine. Dry the inside thoroughly, then the outside. Hang the drysuit on a chunky hanger, not a metal hanger as it can stretch or cut the material. Use a brush or old toothbrush to clean any dirt or dried zipper lubricant from the zipper teeth. Use soapy water to wash the latex or silicone wrist and neck seals.
Undergarments are what keep you warm inside the drysuit, layering light and heavy items depending on the water temperature. Undergarments include full body suits, pants, sweaters, gloves, socks.
Fleece, wool and synthetics are all ideal for use under your dry suit and will retain warmth even if wet. Cotton is not recommend as it will not remain warm when wet and will not dry quickly.
Some dry suit under garments have recommended temperature ranges. These are a guideline only. Be aware of your personal needs and have multiple layers to add or remove as necessary.