Like a Rock

For the last 50 years wetsuits have been made from neoprene, a petroleum-based rubber filled with nitrogen to create an insulating barrier against cold water. Neoprene has about a 70 percent water impermeability, which makes a two-to-three-millimeter-thick suit comfortable to wear in 60-degree-or-higher water. However, in colder water, neoprene suits cannot provide sufficient insulation unless they are up to five or even seven millimeters thick. Thick neoprene suits restrain swimming performance in the water, forcing surfers to choose between being either cold and flexible or warm and immobile.