You know that moment when it's time to get the kids out of the pool so you can head home and have dinner, but they're in the middle of playing with their friends and having a good time? Yeah, you know that's not going to go well.
I don't remember exactly when we started doing it, (UPDATE: It was because of this video) but giving time hacks to the kids for how much time they had left until it was time to wrap it up has alleviated an immense amount of stress in our life.
It's a call-and-response pattern that ensures that the kids have heard the time. I'll get their attention and call out loudly, "Fiiive minutes!" They're then expected to call back, "Fiiive minutes!" If they don't call it back to me, I'll call it out again and again until they do.
You can see the time hack in action at 0:15 into the video above. The jump masters call out "Ten minutes!" and the jumpers respond back to confirm that they've heard and are ready.