Hmm - I must have got an obvious one where the drowning child started flailing his arms desperately trying to stay above water, splashing a lot, which isn't what people do according to the description.
I think this is obvious to some people and non-obvious to others. For example, look at all the people in the video who didn’t rescue the kid.
source: I was once the only person, out of plenty adults outside a pool watching, to notice that one of the two people in the pool was struggling to keep their head up. This includes the kid’s mom, who was giving the kid vaguely encouraging suggestions from outside the pool. I thought it was obvious, apparently no one else around did, and I’ve never had any lifeguard training.
Interestingly, the other person in the pool was the kid’s older brother. He also thought the kid needed rescuing, but he wasn’t nearly a good enough swimmer to help, and he was starting to get into trouble himself by trying to help pull the kid to the side of the pool.
