Wetsuit

A wetsuit is a specialized garment designed to provide thermal protection for people in water. It is primarily used by surfers, divers, windsurfers, and canoeists. Beyond keeping a person warm, wetsuits offer several secondary benefits. They protect the skin from abrasion and ultraviolet exposure from the sun. They can also guard against stings from various marine organisms. Additionally, the material used in these suits provides extra buoyancy, which helps a person stay afloat.

The core mechanism of a wetsuit relies on a material called foamed neoprene. Neoprene is a synthetic rubber that contains many tiny bubbles of nitrogen gas. These gas bubbles are essential because nitrogen has a very low thermal conductivity. Thermal conductivity is a measure of how easily heat moves through a substance. Because the gas is trapped in small, enclosed bubbles, it prevents heat from moving through convection. This forces heat transfer to happen mainly through conduction, which is a much slower process. This setup traps a layer of warmed water between the suit and the skin. This trapped water stays warm because the gas bubbles block the cold surrounding water from taking that heat away.

However, the effectiveness of a wetsuit changes depending on the environment. In still water, heat moves away from the body 20 to 25 times faster than in still air. This happens because water conducts heat much more efficiently than air. While uncompressed neoprene foam provides good insulation, depth changes its properties. At a depth of about 10 meters, the water pressure begins to compress the gas bubbles. This compression can halve the thickness of the neoprene. As the bubbles shrink, the thermal conductivity increases by about 50%. Consequently, a person may lose heat at three times the rate at the surface compared to when they are deep underwater.

Wetsuits are manufactured in various types to suit different temperatures and activities. A "shortie" is a thin suit, often 2mm or less, that covers only the torso, upper arms, and thighs. For much colder water, divers may use a thick 8mm semi-dry suit. These heavy-duty suits usually cover the entire body and are paired with neoprene boots, gloves, and hoods.

A "semi-dry" suit features improved seals at the neck, wrists, and ankles to prevent flushing. Flushing occurs when cold water enters the suit and replaces the warm water trapped against the skin. To prevent this, manufacturers use techniques like gluing, taping, and blind-stitching to create waterproof joints.

The history of the modern wetsuit began in 1952 with physicist Hugh Bradner. While working at the University of California, Berkeley, Bradner realized that a thin layer of water could be kept warm against the skin. He understood that the gas in the fabric, not the water itself, provided the insulation. An engineer named Willard Bascom suggested using foamed neoprene as the ideal material for this design. Although they struggled to market the invention, others turned the idea into a major industry. Jack O'Neill founded a successful company in a San Francisco garage in 1952. Meanwhile, Georges Beuchat invented the "isothermic" sponge-rubber suit in Europe in 1953.

Buoyancy is another critical factor influenced by the physics of the suit. Because foamed neoprene contains gas, it is very buoyant and helps a person float. However, this buoyancy is lost as the wearer descends. Data shows that about 30% of the surface buoyancy is lost within the first 10 meters of depth. By 60 meters, approximately 60% of the buoyancy is lost. The volume of the suit eventually stabilizes after a 65% loss at about 100 meters.

Because of this, scuba divers must use a buoyancy compensator to inflate and maintain their position. They may also need to carry extra weights to reach neutral buoyancy. For an average person, a 6mm wetsuit might provide about 6 kg of net buoyancy at the surface.

It is important to distinguish a wetsuit from a dry suit. A wetsuit allows a small amount of water to enter the suit, relying on a snug fit to limit circulation. In contrast, a dry suit is designed to keep water out entirely. Dry suits keep the wearer's undergarments dry, which helps preserve their insulating effectiveness. Dry suits are typically more complex and expensive to use. They are often required when dealing with extremely low temperatures or contaminated water. While wetsuits are perfect for warm to moderately cold water, dry suits provide a different level of specialized protection.