A swimsuit, bathing suit or swimming costume is an item of clothing designed to be worn while participating in water sports and activities such as swimming, water polo, diving, surfing, water skiing. In New Zealand English and some areas of Australian English, swimsuits are usually called togs or bathers. This term is less common in other parts of the Commonwealth where it can also refer to clothes in general. Swimsuits can be skin-tight or loosely fitting and range from garments designed to preserve as much modesty as possible to garments designed to reveal as much of the body as possible without actual nudity. They are often lined with a fabric that prevents them from becoming transparent when wet.

Swimsuits are designed to cover intimate bodily areas of men and women, subjects that have changed during different eras.

Swimsuit types

Men's swimsuit styles are swimming trunks such as boardshorts, jammers, speedo-style briefs, thongs, g-strings or bikini.

Women's swimsuits are generally either one-pieces, bikinis or thongs. The most recent innovation is the burqini, a more modest garment designed for Muslim women; it covers the whole body and head (but not face) in a manner similar to a diver's wetsuit. These are an updated version of full-body swimwear, which has been available for centuries, but complies with Islam's traditional emphasis on modest dress. In Egypt, the term "Sharia swimsuit" is used to describe full-body swimwear.

Special swimsuits for competitive swimming, designed to reduce skin drag, can resemble unitards. For some kinds of swimming and diving, special bodysuits called diveskins are worn. These suits are made from spandex and provide little thermal protection, but they do protect the skin from stings and abrasion. Most competitive swimmers also wear special swimsuits including partial and full bodysuits, racerback styles, jammers and racing briefs to assist their glide through the water and gain speed advantages (see competitive swimwear).

Swimming without a bathing suit is a form of social nudity. Special nude beaches may be reserved for nude sunbathing and swimming. Swimming in the nude is also known by the slang term "skinny-dipping". As an alternative to a bathing suit, some people use their trousers, underpants or T-shirt as a make-shift swimsuit. At beaches, norms for this tend to be more relaxed than at swimming pools, which tend not to permit this because underwear is unlined, may become translucent, and may be perceived as unclean. For pre-pubescent girls leaving the chest uncovered is sometimes considered unacceptable.fact: date=April 2009

Swimsuits are also worn for the purpose of body display in beauty pageants. Magazines like Sports Illustrated's annual "swimsuit issue" feature models and sports personalities in swimsuits.

Competitive swimwear

Unlike regular swimsuits, which are designed mainly for the physical appearances, competitive swimwear is manufactured for the purpose of aiding athletes in swim competitions. They reduce friction and drag in the water, increasing the efficiency of the swimmer's forward motion. The tight fits allow for easy movement and are said to reduce muscle vibration, thus reducing drag. Starting around 2000, in an effort to improve the effectiveness of the swimsuits, engineers have taken to designing them to replicate the skin of sea based animals, sharks in particular.