They are trained from birth.
They slip out of their mothers 2 metres underwater and have to surf their way to shore on the placenta.
Once you've mastered surfing the shorey on a placenta with a built in leg rope you know your place in the universe.
I think it's called a lot of spare time 
not to mention youthful exuberance
the illusion of indestructibility
and teenage testosterone levels
if you sailed for 5 hours a day from the age of 7 to 16 you would be this good as well
...amazing!
