Swimming strokes should create the least possible water resistance; there should be a minimum of splashing so that forward motion is smooth and not jerky. The stroke most commonly used to attain speed is the crawl, standardized in Australia (hence sometimes called the Australian crawl) and perfected in the United States. In the crawl the body is prone; alternating overarm strokes and the flutter kick are used, and the head remains in the water, the face alternating from side to side. The trudgen stroke (named for an English swimmer whose speed made it famous), also involves alternate overarm strokes in a prone position, but a scissors kick is used and the head remains on one side. The backstroke is done in a supine position and in racing requires alternate over-the-head arm strokes and a flutter kick. The elementary backstroke involves alternation of the frog kick with simultaneous strokes of the arms, which are extended at shoulder level and moved in an arc toward the hips. The sidestroke, a relaxed movement, entails a forward underwater stroke with the body on one side and a scissors kick. The breaststroke can also be a restful stroke and is accomplished in a prone position; frog kicking alternates with a simultaneous movement of the arms from a point in front of the head to shoulder level. The most difficult and exhausting stroke is the butterfly; second only to the crawl in speed, it is done in a prone position and employs the dolphin kick with a windmill-like movement of both arms in unison. It is mastered by only the best swimmers. The dog paddle, a very simple stroke that takes its name from the way a dog swims, is done by reaching forward with the arms underwater and using a modified flutter kick.
In freestyle swimming any stroke may be used, but the crawl, considered the speediest, is almost always favored. No matter what the stroke, breathing should be easy and natural, since the specific gravity of the human body, although it varies with the individual, is almost always such that the body floats if the lungs are functioning normally. In races, facility in diving from a firm surface is essential, except in the backstroke.