Is swimming exercise?

I took the three kids to the gym to use our pool which is open on Sundays. Unfortunately the pool is 4ft everywhere and my youngest just isn't quite tall enough to be ok on his own. He is old enough to be dangerous. I did find time to do a couple laps and wow I felt it on my knee. Maybe I will try at least once a week to add it to my schedule. I guess I can handle once a week, wet swimming suit/hair in the middle of winter isn't on the top of my list of to-do's. Well got to go play Blokus with my youngest. Dinner is in the oven, what better thing to do.