When I teach my little ones to to swim, starting at about 2 years, I warn them about not getting in over their head. I teach them how to hold their breath and float.
Eventually I take a break. I’ll park them on the pool steps (anybody remember those?) and admonish them not go go off the steps.
Then I’ll sit a few feet away and watch them like a hawk. Eventually they….step off the step. I walk up to them, look down at them under the water, looking up at me, shocked, pull them out, park them on the steps again, and say, “Do not go off of these steps.”
They never do it a second time.
They need to find out how dangerous water can be. They need to find out for themselves and I’d rather they find out in a situation where I have control rather then at a moment I’m not looking.
But…they’re pretty much swimming by the end of that first day. I mostly teach them how to rescue themselves, like, hopping up and down in water over their head until they get to shallower water.