I would think that for most of us, it can be defined as sport. Some people that know us will call it other things
... Maybe to the guy that drifts worms twice a year, it's probably just recreation or a sanity check.
To me, it really is more than just sport though. It's adrenaline, sweat, salt, & scales all mixed in with beauty, serenity, and the undescribable way that the sound of the surf can melt away about everything that may have bothered me that day or week... Just not describable by my meager capabilities....