First and foremost, the adult in the
water with the child (preferably the mother if the child is an infant - she has already established the necessary bond with the infant) should be a swimmer, comfortable and confidant in the
water.
As a senior physician and someone more aquatic than terrestrial, I disagree with age restrictions suggested by
medical authorities. For the child (infant?), the younger the better. We are all born with a
diving reflex which keeps us from inhaling when our face is immersed. This reflex is usually estinguished during the first year of life.
I suggest starting within a few days after birth, making bathing in the tub something pleasureable for the child and parent. An infant of even a few days of age can be taken into a pool for play, and within the first few months, can be dunked. This is best done by gently bobbing the infant, gently blowing into the infant's face, and then very briefly dunking the infant. It should be a
game, and should be interrupted any time the infant appears uncomfortable. Most infants will initially show surprise rather than discomfort, and then rapidly become comfortable with their face immersed.
Then a progression to rising to the surface and floating can be initiated, taking advantage of the infant's net bouancy and reflexive efforts to stroke to the surface. Somewhere around 6 months, "drown proofing" can be started, by releasing the child very close to the edge of the pool and letting natural instincts lead "him" to the edge of the pool
deck. Then successively release "him" a bit further away from the edge, and natural stroke development is initiated.
Between 3 and 5 years, formal stroke instruction can be initiated, progressing from "dog paddling" to a beginning freestyle stroke.
My caveats echo that of most other posters.
There must be a capable adult swimmer immediately beside any child who has not mastered a freestyle stroke. A life jacket must be worn at all times when a child is playing on the
dock or onboard the
boat, and even then an adult swimmer must be in constant attendance. Education, based in information rather than fear, in water
safety is essential.
Swim aids like arm floats or flotation clothes only delay
learning to swim and should be avoided. Life jackets are
safety devices for use when at the child is at risk, but do not help during efforts to introduce the child to swimming.
Our
children were in the pool at a few days of age, were pool safe by 6 months, and could swim across the pool by the time they started walking. Now they are like my wife and me, more aquatic than terrestrial.