A wetsuit is a special suit worn by people who want to spend a lot of time in the water. Wetsuits are usually worn by swimmers, divers, or surfers who swim in cold water. Wetsuits insulate the swimmers, or help them retain body heat. This, in turn, helps the swimmers avoid hypothermia, a dangerously low body temperature.

Wetsuits are made of a kind of rubber called neoprene. The suit traps a thin layer of water between the neoprene and the wearer’s skin. So, the wearer is always wet—that’s why it’s called a wetsuit. Body heat warms the layer of trapped water and helps keep the wearer warm. The wetsuit must be tight, or else the layer of water between it and the wearer’s body will be too wide to keep warm.

The suit can cover the whole body, or just a swimmer’s legs or torso. Hoods, jackets, and vests can be added for extra protection.

There are different thicknesses and styles of wetsuits to fit different water conditions and the wearer's needs. Usually, the thicker the wetsuit, the warmer it keeps the wearer. However, the thicker the wetsuit, the more difficult it is to move in it. Most wetsuits are between 3 and 5 millimeters thick.

Swimmers and divers who spend time in icy waters, however, don’t wear wetsuits. They wear drysuits, which do not allow any water to penetrate them. All divers in the Arctic and Antarctic wear drysuits.

Because wetsuits offer protection against jellyfish stings and rocky reefs, many swimmers choose to wear them in warm water. The "shorty" wetsuit, covering the wearer’s torso with short sleeves and short leggings, is a common sight on warm surf beaches from Australia to Southern California.

As with many inventions, there is a dispute over who made the first wetsuit. Dr. Hugh Bradner, an American physicist who loved to dive, may have made the first wetsuit out of neoprene in 1952. He wanted to find a way for divers to avoid hypothermia and still be able to move freely in the water.

Other inventors sought the same goals. Jack O’Neill was a surfer who in the 1950s was also looking for a way to stay in the water longer. He experimented with different combinations of rubber suits, finally hitting on neoprene. It was flexible and a good insulator. O’Neill began to make neoprene wetsuits for himself and other California surfers. He set up a shop on the beach and grew his business into what is today a multi-billion-dollar industry.