I spent my childhood around pools, lakes, the ocean, etc. My parents signed me up for swimming lessons when I was crawling. I completed lifeguard training, and was certified as a red cross Water Safety Instructor. I taught swimming lessons for 6 years (most of high school and college).
Swimming is an important life skill, and GREAT exercise for cfers. The rythmic breathing pattern of freestyle help me get up tons of crap, and kept my airways open better than any other exercise out there. I don't swim as much as I should - pool access is a challenge, and I like biking and running more, but I know I should, and I'm thrilled I have the know how to pick it back up if/when the pool access issue improves.
PA grows everywhere. Do you really expect you or your kid to never take a shower, never go in a pool or lake??
To not let your CFer swim because they have CF is letting CF win. It tells them that CF is a reason not to do things, and in my opinion, that is terrible message to send them. If you want your CFer to push themselves to succeed in all walks of life, but more importantly, to succeed in beating CF, they have to believe they can do anything they set their minds to. You don't learn to fight by being kept out of the ring.
To tell a kid "you can't do this because you have CF" will discourage them, and teach them that it is OK to use CF as an excuse to not do things. It will also make them feel like they are less able than their peers, affect their self-esteem, and make them more likely to rebel against compliance with their CF routine.
Obviously many people with CF do have some limits to their physical abilities, but it is important that they discover those limits themselves instead of having them imposed by their parents or docs. If you raise them and forget to tell them that they are "supposed" to have limits, they may surprise you...
Chris
27 m w/cf