children like him enjoy the water (oh well, they were surrounded by water in our wombs for 9 months remember?). it provides gentle muscle training and strengthens the heart and the lungs. and even if it is often an individual sport, kid swimmers can also join competitive swim teams (in gensan, they call the famous swim team -TORPEDO), making swimming a sport your kids can enjoy wether alone or as part of the team. and yes, not to overemphasize, wowa was somewhat overweight but since he found swimming to be a pleasure, he lost some of his baby fats without feeling weary and without compromising his diet.
but of course, parents should always be on guard and be aware of 'safety swimming' - give the kids proper coaching (lessons from a pro) to orient them on the swimming gadgets (goggles, flippers, swim cap among others) and proper swimming techniques. parents too should be aware of the possible risks of swimming to kids like the possibility of an ear infection, (see related blogpost here-- http://sakura-withdrawalpangs.blogspot.com/2010/07/wishing-hed-say-goodbye-to-swimming.html ) which may be both painful and inconvenient to your swimming kid. this specific infection however may be treated with antibiotics and there are ways of preventing it such as the one given here --http://www.mayoclinic.com/health/childrens-health/CC00003 . so there you go. swimming may be one of the best options for kids' health and fitness there is, worked for my wowa.