My little one went to water babies from a few months old, they have a technique that they do beforehand whereby baby knows when its happening, (certain part of a song) and they do it when the baby is confident and the parent also. I was useless as not confident, and i think that's important. If they not keen best not too, could scar them for ages afterwards. One teacher (not waterbabies) used to let them dunk when they had a cold, as it decongested them, must say it did work.