A one-piece swimsuit is a usually skin-tight one-piece swimsuit worn by women and girls when swimming in the sea or in a swimming pool, or for any activity in the sun, such as sun bathing. The one-piece swimsuit usually covers a female's torso. Some women wear a one-piece swimsuit because they consider it to be more modest than a two-piece bikini.
Before the popularity of the two-piece swimsuit, and then the bikini, virtually all female swimsuits were one piece, and men also wore similar swimsuits that covered their whole torso.
The most common type of one-piece suit is the maillot or tank suit, which resembles a sleeveless leotard or bodysuit. Variants of this include halterneck and plunge front swimsuits, as well as wrap-round ("surplice") and bandeau styles. The pretzel suit is another special case of the one-piece swimsuit.
Recently, athletic swimsuits have used a variety of new shoulder strap styles, including the racerback, fastback, and flyback styles, some of which have also been used on other athletic wear.
Another recent innovation in one-piece swimsuits is the bodyskin, which superficially resembles a unitard or wetsuit. Although these cover the entire torso, arms and legs, their function is not modesty, but reducing friction through the water for professional swimmers. Their surfaces are made of textured technical fabrics which are engineered to cut through the water in the same way as fish or shark skin.