I find it interesting that humans can hold their breath and undertake rudimentary locomotive swimming with in a few weeks weeks after birth it is considered an evolutionary response.
Yes it is amazing, and it is true that most animals seem to know how to swim without any learning involved.
I love swimming. THe human body is less dense in water and water supports the weight of the body.
Is that what they call buoyancy?,  I enjoy swimming too but I think I prefer just to float. 
True. Higher levels of body fat and the more salt in the water lowers the density of the body and increase buoyancy.
Yes floting works better at see and yes I have my fair amount of body fat At what age did you learn to swim?
Swimming is one of the top public recreational activities. and in different countries they add it as an extra curricular activities.
And it is a good sport too, even when I don't think  would enjoy it that way.  That's one of the reason I don't think I will ever compete in a triathlon, that involves swimming, running and biking. 
I learned to swim at 3 years old. Swimming is the self propulsion of one through a body of water for recreation sport or exercise.
I don't rememeber at what age I learned, probably around that age, certainly not as a baby like some people do.  Anyway everyone should know how to swim, if only for safety reasons..