On December 26, 2004, a 9.1 to 9.3 magnitude earthquake struck the Indian Ocean off the coast of Sumatra. The resulting tsunamis devastated the coastal regions of the area, as seen above (via India Today). And the loss of life was enormous, with a total death toll exceeding 200,000 people. And yet, it could have been worse, if it weren’t for Tilly Smith — a ten-year-old girl.

On that day, Tilly Smith and her family — her parents and a younger sister — were on vacation at a resort on Maikhao Beach in Phuket, Thailand. As her mother would later tell National Geographic, something odd began to happen while the family relaxed on the beach: “The water was swelling and kept coming in. There was froth on it like you get on the top of a beer. The sea was like a millpond before [the swelling began].” It was like something none of them had ever seen — but one of them had recently learned about.

Tilly, at the time, was an elementary school student from Surry, England. Just two weeks prior to her family’s vacation, her teacher, Andrew Kearney, had taught a lesson on tectonic plates, oceanic earthquakes, and, luckily for those on the beach that day, tsunamis. When the water began to foam up, Tilly — recalling her recent lesson — noticed, and told her parents.

At first, they ignored her, per ABC News, but she persisted and “finally convinced her father, Colin Smith, to turn back to their hotel, where he approached a security guard stationed on the beach.” The security guard heeded the warning and ordered the beach and surrounding areas evacuated. The hundred or so people who would have been in the path of the tsunami instead retreated to the hotel, far enough away to stay clear of harm — all because a ten-year-old paid attention in school and had the presence of mind to sound the alarm.

The young Miss Smith, in honor of her efforts, was named Child of the Year by French youth magazine Mon Quotidien and has an asteroid named after her.