Baby swimming classes

would advise to start sending before 18months if keen. takes a few sessions for kid to get used to it. I've sent my kid at 18months (for 2 months of swimming) and she cried bloody murder but as compared to kids in the same class who started earlier, they seem more confident in the water. now kid is 3.5 yo and restarting swim classes, she's also more confident after her 2nd month and looks forward to lessons!