The entire body must be used to move through the water in the racing sport of swimming, which can be done individually or in a team. The sport is played in open water or in pools. With a variety of distance events in the butterfly, backstroke, breaststroke, freestyle, and individual medley, competitive swimming is one of the most popular Olympic sports. In addition to these individual competitions, a freestyle or medley relay is an option for four swimmers. Each of the four swimmers in a medley relay will swim a different stroke, such as the backstroke, breaststroke, butterfly, or freestyle.