is an individual or team sport that uses arms and legs to move the body through water. The sport takes place in pools or open water (oceans, lakes etc.). Competitive swimming is one of the most popular Olympic sports, with varied distance events in butterfly, backstroke, breaststroke, freestyle, individual medley. In addition to these individual events, four swimmers can take part in either a freestyle or medley relay. Swimming each stroke requires specific techniques, and in competition, there are specific regulations concerning the acceptable form for different strokes. There are also regulations on what types of swimsuits, caps, jewelry and injury tape are allowed at competitions. Although it is possible for competitive swimmers to incur several injuries from the sport -- mostly shoulder related -- there are also multiple health benefits associated with the sport.
Competitive swimming became popular in the 19th century. The goal of competitive swimming is to break personal or world records while beating competitors in any given event. Swimming in competition should create the least resistance in order to obtain maximum speed. However, some professional swimmers who do not hold a national or world ranking are considered the best in regard to their technical skills.

World Championship pools must be 50 metres long and 25 metres wide (also known as long course), with ten lanes labelled zero to nine (or one and ten) the lanes must be at least 2.5 metres wide. They will be equipped with starting blocks at both ends of the pool and most will have Automatic Officiating Equipment, including touch pads to record times and sensors to ensure the legality of relay take overs. The pool must have a minimum depth of two metres.
Other pools which host events under FINA regulations are required to meet some but not all of these requirements. Many of these pools have eight instead of ten lanes and some will be 25 metres long (short course). World records that are set in short course pools are kept separate from those set in long course pools because it may be an advantage or disadvantage to swimmers to have more or less turns in a race.