I was invited to a birthday party to a swimming hall and couldn't swim. Nobody admits that. So i walked off, got into the warm, outside bubble pool, that had a sloping floor, and walked in, on my toes. Then the foot slipped. Almost drowned, saved by an adult.
Same thing happened to me when I was 5 or 6. I was at a neighbors swimming pool in the shallow end but it had a very steep slope to the deep end, got a little too close and down I went. No one noticed, sounds strange but like the videos show, it happens. Another kid, a teen at the time, ran from inside the house jumped over a table and dove in and pulled me out. Heh he was treated like the hero he was for the rest of the day by the grown ups.