Around 6 months for a public pool, and the binding constraint is water temperature rather than age.
| Age | Minimum water temp | Time in |
|---|---|---|
| Under 6 months | 32°C / 90°F | 10 min |
| 6–12 months | 30°C / 86°F | 20 min |
| 1–2 years | 29°C / 84°F | 30 min |
| 2 years+ | 27°C / 81°F | 30–40 min |
Why temperature is the real limit
A baby has a large surface area relative to body mass, very little insulating fat, and an immature ability to shiver — which is the main way a body generates heat when cold.
That combination means a baby loses heat in water several times faster than an adult and cannot recover it efficiently. Hypothermia in a pool that feels merely cool to a parent is a genuine risk, and it develops quietly.
Most public pools run at 27 to 29°C / 81 to 84°F, which is too cool for a baby under six months. Dedicated baby or hydrotherapy pools run warmer, which is why baby swimming classes are held in them.
Watch for shivering, blue lips or fingertips, or unusual quietness. Get out at the first sign — a baby who has stopped protesting about the cold is not more comfortable.
Chlorine and vaccinations
There is no requirement to wait for any particular vaccination before swimming. That advice circulated widely and is not part of current guidance from paediatric bodies in either the US or the UK.
Chlorine at normal pool concentrations is not harmful to babies. Rinse afterwards and moisturise, since chlorinated water dries skin — and babies with eczema often need a barrier cream before going in as well as a moisturiser after.
A baby with an open wound, an ear infection, or diarrhoea in the previous 48 hours should not swim. That last one is a public health rule as much as a personal one.
Swim nappies do what, exactly
A swim nappy contains solids. It does not absorb urine, and it is not designed to — an absorbent nappy in water swells with pool water and becomes useless and heavy.
Double up: a disposable swim nappy under a reusable neoprene one is the standard approach, and most pools require it for children not reliably toilet trained.
Change it immediately afterwards. A swim nappy left on holds moisture against the skin and causes rashes quickly.
Supervision is the only rule that has no exception
Touch supervision — an adult within arm's reach, in the water, undistracted — for every child under five, every time, regardless of any swimming lessons taken.
Drowning is silent and fast. It does not look like the splashing in films; a drowning child cannot call out because the airway is prioritising breathing.
Formal swimming lessons from age one can reduce drowning risk and are recommended by the AAP, but they do not replace supervision and no child under five should ever be considered water-safe.
Home pools and paddling pools
The same temperature rules apply, and a garden paddling pool in sunshine can go from too cold to genuinely too hot within an hour — check it rather than assuming.
Empty it immediately after use. A young child can drown in a very small depth of water, and standing water is also a hygiene problem within a day.
Sun protection matters more in water than out of it, since reflection roughly doubles exposure. Babies under six months should be kept out of direct sun entirely rather than relying on sunscreen.
Safe sleep rules and car seat limits follow the same pattern — the published number is a floor, and supervision is what actually does the work.
Sources: American Academy of Pediatrics guidance on swim lessons and drowning prevention; NHS Teaching your child to swim.
General reference, not medical advice.