I enjoy swimming, it's among the top public recreational activities and it keeps me in shape
I love to swim and its a low impact way to get some exercise. how long have you been swimming?
Since I was a young child. I swim for exercise, though many swim for recreation, sport, and even survival 
I love to watch competitive swimming, have you ever done that?
I don't watch many national or international competitions, but I usually watch swimming during the summer Olympics
I like that swimming is low impact on my joints I can swim for hours without being in pain
Yes it's great for that. It's much more 'low-impact' compared to land activities like running, so it's better for your joints
Its good exercise for lung disease as well I can exercise without getting winded