Swimming is the self-propulsion of a person through water, or other liquid, usually for recreation, sport, exercise, or survival.
Swimming relies on the nearly neutral 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. However, buoyancy varies on the basis of body composition, lung inflation, muscle and fat content, centre of gravity and the salinity of the water. Higher levels of body fat and saltier water both lower the relative density of the body and increase its buoyancy. Human males tend to have a lower centre of gravity and higher muscle content, therefore find it more difficult to float or be buoyant.