well nudediver, i didn't want to be adversarial, but here we go.
i don't quite understand how you can say that defining a sport goes well beyond having to be in shape, and then turn around and define sport as needing a higher degree of athleticism and involving competition, where in both of those you need to be in shape. how many people with a higher degree of athleticism do you know who are not in shape? how often to people sign up to compete in something, when they are totally out of shape. nope, you confused me a bit on this one my friend.
actually a sport is defined as:
Sport: is an activity that is
governed by a set of rules or customs and
often engaged in competitively.
the problem with your argument is that we can't just make up whatever definition we want for words. words have official definitions, accepted worldwide and they are pretty concrete. under the official definition of the word sport, scuba diving definitely applies.
...and just to be totally
contradictory, i don't consider golf as much of a sport either!!