A wetsuit is a tight-fitting rubber suit that keeps swimmers, surfers, and divers warm in cold water. The suit works in a clever way: it allows a thin layer of water to seep in between the suit and your skin, and your body heat warms that trapped water, creating an insulating layer that helps keep you comfortable even in chilly ocean water.

Wetsuits are made from a synthetic rubber called neoprene, which contains tiny air bubbles that provide extra insulation. The thickness of the suit varies depending on how cold the water is. A surfer in California might wear a thin wetsuit, while a diver exploring frigid Alaskan waters needs a thick one. The suit fits snugly so that water doesn't constantly flow in and out, which would wash away your body heat.

Without wetsuits, activities like surfing, scuba diving, and ocean swimming would be miserable or even dangerous in many parts of the world. Before wetsuits were invented in the 1950s, divers who stayed underwater too long risked hypothermia, a dangerous drop in body temperature. Today, wetsuits let people safely explore and enjoy cold waters that would otherwise be off-limits.