Every parent fears losing track of their child, but they wouldn't be so scared if everyone worked together the way beachgoers in Brazil did after finding a kid who'd gotten separated from his family.
When a man noticed that the young boy seemed lost, he started to clap and got everyone around him to clap as well. The noise alerted all parents nearby to check on their children and the one mom who didn't see hers knew exactly where to go to find him by just following the clapping.
According to one South American commenter on YouTube, the technique is used in Argentina, Uruguay and Brazil and usually what happens is a mother who can't find her child, or a child who can't find his family, will get a group clapping to help them reunite. The lost child is often lifted onto the shoulders of the tallest person in the area.
If this video is any proof, it seems to work pretty well!