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
Obviously it's exercise, so it's good for the body. It's also a low impact activity compared to other exercises like running.