My son had a "near drown experience" at ~2yo with a swim ring in a pool.

He somehow jumped from the side and "capsized" ending up with his head underwater, so the ring kept him in that position.

I was playing with my daughter facing the other direction and didn't notice until she pointed him out, I fished him out and he had somehow kept his breath (it was some seconds, not minutes) and kept playing as if nothing happened soon after.

I was scared shitless.

I've been paranoid about my kid around water when he was younger, mostly because this was advice given by my father to me when I was an adolescent, in some context where I was going to be partially responsible for children:

Little kids can drown in as little as 2 inches of water. They can drown a bathtub that's mostly empty.