@Macrendil Really? I'm sure you've learned yourself, because it's not an innate talent of humans. It's a learned skill, one which many do not have. The simple reason being we don't live in water, people may not have the opportunity to even attempt learning because of the lack of body of water. When given the chance at an older age, many refuse to learn out of simple embarrassment.
Personally I had a terrible experience learning to swim because my father was a psychopath. I did learn, but I haven't swam in so many years I'm unsure if I still can.