When can I bring my baby to public Swimming pool?

My baby was 4 months old when she started swim lessons. She loved being in the water from the very onset. Every week we see older babies join the class but most cry uncontrollably the moment they enter the pool, because they're not used to the water. They end up having to leave the pool because they won't calm down. Apparently studies have shown that babies lose that natural affinity with water after 6-9 months so probably best to start earlier.