A wetsuit is a garment, usually made of foamed neoprene, which is worn by surfers, divers, windsurfers, canoeists, and others engaged in water sports, providing thermal insulation, abrasion resistance and buoyancy. The insulation properties depend on bubbles of gas enclosed within the material, which reduce its ability to conduct heat. The bubbles also give the wetsuit a low density, providing buoyancy in water. Hugh Bradner, a University of California, Berkeley physicist invented the modern wetsuit in 1952. Wetsuits became available in the mid-1950s and evolved as the relatively fragile foamed neoprene was first backed, and later sandwiched, with thin sheets of tougher material such as nylon or later Lycra/Spandex. Improvements in the way joints in the wetsuit were made by gluing, taping and blindstitching, helped the suit to remain waterproof and reduce flushing, the replacement of water trapped between suit and body by cold water from the outside. Further improvements in the seals at the neck, wrists and ankles produced a suit known as a “semi-dry”. Different types of wetsuit are made for different uses and for different temperatures. Suits range from a thin (2 mm or less) “shortie”, covering just the torso, to a full 8 mm semi-dry, usually complemented by neoprene boots, gloves and hood.