A wetsuit is a garment, usually made of foamed or compressed neoprene, which is worn by divers, surfers, windsurfers, canoeists, and others engaged in watersports. They give thermal insulation, abrasion resistance and buoyancy. The insulating properties are caused by bubbles of gas enclosed within the material, which reduce its ability to conduct heat. The bubbles also give the wetsuit a low density, giving buoyancy in water. Contrary to popular belief, the layer of warm water normally trapped between the wetsuit and the skin provides very little thermal insulation.
Semi-dry suits are effectively a thick wetsuit with better-than-usual seals at the wrist, neck and ankles. The seals limit the volume of water entering and leaving the suit. The wearer gets wet in a semi-dry suit, but the water that enters is soon warmed up and does not leave the suit readily, so the wearer remains warm. They are made from thick neoprene, which provides good thermal protection, however some buoyancy and thermal protection is lost when the bubbles compress at depth. Semi-dry suits come in various configurations, e.g. a single piece or two pieces made of long johns and a separate jacket. Semi dry suits do not usually include boots, so a separate pair of insulating boots are worn. These suits are typically used where the water temperature is between 10 and 20 °C (50 and 68 °F).
