Swimming is the self-propulsion of a person through water or another liquid, usually for recreation, sport, exercise, or survival. Locomotion is achieved through coordinated movement of the limbs, the body, or both. Humans can hold their breath underwater and undertake rudimentary locomotive swimming within weeks of birth, as an evolutionary response.

Swimming is consistently among top public recreational activities and in some countries, swimming lessons are a compulsory part of the educational curriculum. As a formalized sport, swimming features in a range of local, national, and international competitions, including every modern summer Olympics. Swimming relies on the natural buoyancy of the human body. On average, the body has a relative density of 0.98 compared to water, which causes the body to float.