This is, frankly, a rather silly discussion in which people compare their own personal definitions of a word (sport). It has nothing to do with the activity itself. You are not arguing over scuba; you are arguing over how you define the word sport. In that case, no one can be wrong, and no one can be right, because you are all using your own personal definitions.
As many have pointed out, the word sport has been used many times over the centuries to include activities that would easily include scuba. Pick up a copy of Sports Afield magazine and see what their definition of a sportsman is. Ask yourself why betting on the winner of a horse race is called "the sport of kings."
This discussion is better suited to a web site devoted to a discussion among lexicographers on the evolution of the meaning of words, if such a site exists.
With that sort of attitude 80% of the board traffic would be eliminated!
IMO this discussion is one about perspectives with no right answer.