Drysuit

A waterproof suit with seals at the neck and wrists that keeps the diver dry, insulated by undergarments and inflated with gas at depth.

A drysuit does exactly what the name says: it keeps the water out. Watertight zippers and seals at the neck and wrists mean you dive in an envelope of air, with warmth coming from insulating undergarments worn underneath rather than from the suit shell itself. Drysuits are the standard choice for water below roughly 15 C, for ice diving, and for long technical exposures where a wetsuit would leave you dangerously cold.

Because the air inside compresses as you descend, a drysuit has an inflator valve fed from your tank and an exhaust valve, usually on the upper left arm, to vent expanding gas on ascent. You manage two air spaces, suit and BCD, which changes your buoyancy workflow enough that agencies teach a dedicated drysuit specialty covering weighting, venting, and recovering from an inverted feet-up position.

Shell suits made of trilaminate fabric are light and dry fast, while neoprene drysuits add some inherent insulation. Seal care, zipper wax, and proper storage are what keep an expensive drysuit dry for many seasons.