When your child is 3 years old, they are developmentally ready to swim 1:1 with an instructor. Most 3 year olds are able to follow instructions, which is an important skill for learning how to swim and for staying safe in the water.
If your child is 3 years old, but has trouble separating from you, or hasn't spent much time in the water, or seems nervous, it's a good idea to take a Parent & Toddler class before signing him/her up for private lessons.
Swimming lessons for 3 year olds are focused on readiness skills. Children learn basic safety rules, breath control, and basic arm and leg movements. As children get older and become more experienced in the water, they learn more difficult swimming skills.