Kids are developmentally ready for swim lessons when they are about four years old. Prior to that, their brains and bodies just aren't able to coordinate the motions of swimming strokes.
Still, younger children can also benefit from swim lessons that emphasize water adjustment, safety, and swimming readiness skills. (Always remember that swim lessons are never a substitute for direct supervision anytime your young child is in or near water--even the bathtub.)
For infants (6 months and up), toddlers, and young preschoolers, look for a class that follows American Red Cross and YMCA guidelines:
- Instructors should have first aid/resuscitation certification.
- Parents should be in the pool with their children.
- Children should not be required or encouraged to submerge their heads underwater.
When enrolling older children in swim lessons, also look for safety-certified instructors and for a progressive program that allows kids to advance through each level as they master new skills. (Watch a video about how to choose swim lessons.) Swimming is a great workout and offers both an individual and team sports experience.
Source:
American Academy of Pediatrics Policy Statement. Swimming Programs for Infants and Toddlers. Pediatrics Vol. 105 No. 4 April 2000, pp. 868-870 (reaffirmed October 1, 2004).

