I actually spotted that kid as the first possible point of trouble... but you have to wait until the "moments later" card to see him start doing something risky, and then like you said, even when he's tangled in the rope it won't let you click him.
For that guy I waited until he started actually showing IDR signs - no lateral movement, dipping up and down. Even though he's struggling in the rope he's still managing to move around using a bad freestyle.
That thrashing around doesn't look like he's still managing. That's full on panic. As someone that has been on life guard duty, that would be enough for me to dive in and get him out.
