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.
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
Infant swimming
Infant swimming is the phenomenon of human babies and toddlers reflexively moving themselves through water and changing their rate of respiration and heart rate in response to being submerged. The slowing of heart rate and breathing is called the bradycardic response. It is not true that babies are born with the ability to swim, though they have reflexes that make it look like they are. Babies are not old enough to hold their breath intentionally or strong enough to keep their head above water.
Most infants, though not all,