When did people start swimming?
Well, considering swimming is achieved through the motion of limbs, probably since man first walked the earth.
wow that's long
It is indeed. Especially if you're holding your breath while swimming. Any other questions, nitwit?
which country first realized the sport 
That question doesn't even make sense. But, swimming is a competition in the Summer Olympics.
ok, what are the benefits of swimming
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 such as running. The density and viscosity of water also create resistance for objects moving through the water. Swimming strokes use this resistance to create propulsion, but this same resistance also generates drag on the body.
Hydrodynamics is important to stroke technique for swimming faster, and swimmers who want to swim faster or exhaust less try to reduce the drag of the
Swimming
Swimming is the self-propulsion of a person through water, 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 a survival response.
Swimming is consistently among the 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