found this
When can I start swimming with my baby?
Parents used to be advised to wait until their baby had had their immunisations at two, three and four months before they took their babies swimming. But government health experts no longer believe this is necessary, so it's really up to you when you start taking your baby to the pool. "There are no medical grounds for waiting until your baby is immunised. However, most pools start classes at around 12 weeks," says Libby Tucker, a swimming teacher who specialises in parent and child courses. Remember too, that a noisy public swimming pool could be daunting for your newborn, so it may be worth waiting until he's a bit older. You will probably have to wait until you've had your six-week check before you can go yourself, anyway.
i knew there use to be a rule haha i thought i had baby brain