Swimsuits Parade, Sydney, Australia

Some swimsuits are designed specifically for swimming competitions where they may be constructed of a special low resistance fabric. They reduce skin drag, and 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 thus gaining a speed advantage (competitive swimwear).
Unlike regular swimsuits, which are designed mainly for the aesthetic appearances, swimsuits designed to be worn during competitions are manufactured to assist the athlete 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.
In July 2009, FINA voted to ban non-textile (non-woven) swimsuits in competitive events from 2010. The new policy was implemented to combat the issues associated with performance enhancing costumes, hindering the ability to accurately measure the performance of swimmers. Subsequently, the new ruling states that men's swimsuits may maximally cover the area from the navel to the knee, and women's' counterparts from the shoulder to the knee.
Some swimmers use a specialized training suit called drag suits to artificially increase drag during practice. Drag suits are swimwear with an outer layer of looser fabric - often mesh or nylon - to increase resistance against the water and build up the swimmer's endurance. They come in a variety of styles, but most resemble a looser fitting square-cut or swim brief.