The secret of happiness is to live here and now. The fact that a jet skier can't be sad is that because he is concentrated on here and now, and he has no choice (not by choice) but by compulsion.
that means it is not real happiness, but delayed sadness (if he was sad before riding it). But if one realized his self and lived in peace with it, then he will be happy even if was locked inside four walls for a year.
The name of the game is "Self-realization".