One of my granddaughters (who will be 2 next week) has been in one-on-one self-rescue classes. I don't know if there are different kinds of these classes, but she in learning how not to panic if her head were in the water, how to surface and get on her back, and how to get herself to the side of the pool. Her parents have friends with home pools and decided this training would be very worthwhile.
It has been fun to watch the videos. Last summer, as an infant, she fussed big time when she had to do all those things in the water. However, although she fussed, she did them. The teaching was discontinued over the winter because even in Texas an outdoor pool can be too cold. This summer she went back for more. She "fell" into the pool (supervised), righted herself and, instead of crying, she was floating on her back making conversational comments to the teacher! (Was she trying to converse last summer, too?)
I'm so happy that she is learning to handle herself in water in both winter and summer clothes (including shoes) AND with a full diaper.
Her mama tells me they hope to put her in regular lessons later on.
Back in Medieval times, when my own mama registered me for group swim classes, I was well over two years old. But If they had had these rescue classes for kids all those decades ago, I think I'd have wanted to take those first. I might even have learned to swim! I was much too afraid of what *might* happen to do much in class. If I'd known I could handle myself, it might have been great learning to do the proper strokes and build endurance.
But I imagine that if you need to ask someone if the early classes would "ruin" a child for traditional lessons, the traditional-class swimming teacher would be the one to ask.