Swimming should not be considered a sport. Why not? Because a sport is a activity of physical exertion where you can stop your opponent. In the COMPETITION that swimming is, you can not stop your opponent from beating you. Just like track isn't a sport because you can't stop your opponent. Swimming is a in the category of golf, competitive cheer, track and field. You can't stop the person/people you are going up against. You just have to get a better score or be faster than them, whether it is running or swimming. It isn't sport but it is a competition.
Dude seriously? Ever heard of Micheal Phelps? Think about how hard he practices and works to be good. Also, think about this. Swimming is harder than all other sports. Why? Because you have to hold your breath while working out. Try doing that and tell me how it goes and if you can do it then I'll believe you its not a sport.