  thumb|competitive open water swimming race human swimming is the self-propulsion of a person through water or another liquid, usually for the purpose of recreation, sport, exercise, or survival. locomotion is achieved through coordinated movement of the limbs, the body, or both. humans are able to hold their breath underwater and undertake rudimentary locomotive swimming within weeks of birth, as an evolutionary response. swimming is consistently found to be among the top recreational activities undertaken by the public, 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, which occurs every four years. ==science== 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. however, buoyancy varies on the basis of both body composition 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 floatation. since the human body is only slightly less dense than water, water supports the weight of the body during swimming. as a result, swimming is "low-impact" compared to land activities s
Human_power Swimming