A boxer, wrestler, martial artist or team sport competitor may be every bit as superb an athlete as Phelps, but is only allowed one medal per Olympics. Gymnasts, weight lifters and competitors in a few other sports may have four or five events they can compete in, but swimming includes something like 25 possible events. Yes, it's amazing someone can qualify for as many of these as Phelps did, but it doesn't make him a greater athlete, IMHO, than the guy who brings home the gold for bantamweight boxing or cycling's individual road race, or Judo, Taekwondo or tennis.
But it's an easy thing to cover. Just stay at the pool, point the camera, babble some more from your background material (little or none of which was written by you), and wait.
Of course the whole Olympics is kind of that way, everyone covering it has had years to prepare, and all you really have to do is show up.