1.

It's a healthy thing to do!  Ask any doctor and they will undoubtedly say that swimming is one of the best exercises for young and old bodies.

2.

It is a low injury rate sport.

3.

It is available to boys and girls of all ages.  This is actually more important than it seems at first glance.  Most other organized activities tend to segregate by age and sex.  On a swim team, a ten year old girl can be just as important as a sixteen year old boy.  Small boys and girls have equal rights on swim teams, too.

4.

It encourages a more rounded social development.  This is partly related to the above paragraph and swimming becomes a family type activity involving other swimmers, coaches, and parents.  It leads to a much wider circle of friends.

5.

It promotes self-organization and discipline.  Children who choose to swim, generally organize their daily activities due to the tight schedule and this often shows up in the increased ability to focus on specific tasks.

6.

In open meets, Juniors get a chance to swim in the same events as Seniors and Champions in a manner denied in other sports.