I’m surprised at the people who don’t think babies or toddlers should be in a pool. In the UK at least, parent and baby/toddler classes are a common sight. At my local, 25x10m, pool, there isn’t even a separate area, they just rope off the shallow end for the class whilst everyone else gets the rest of the pool.
During the classes kiddie music is played and the babies are mostly held by their mothers or held onto various floating toys. The more adventurous ones are encouraged to try a little free swimming. It’s a good way to get them used to water.
They all wear swim nappies. In all the time I’ve been going, over ten years, only once has there been a pool clearing incident, when a baby was sick. We all got vouchers for a free session. Incidentally my pool offers adult only sessions if you don’t want to share with kids. Kids can be a splashy pain but the toddler classes have never bothered me.