Three years ago, 16-year-old Alex Weber was diving when she spied something strange in the waters off Pebble Beach, California: golf balls. She was concerned, as the balls leach chemicals and shed bits of microplastic into the ocean as they erode, harming marine animals. With the help of family and friends, Weber began cleaning up regularly, gathering at least 500 balls on a typical dive. But every time they dove, the seafloor they’d previously cleared was again blanketed with balls hit by golfers on nearby courses. Hoping to get people to change their behavior, Weber worked with a biologist at Stanford University to co-author a research paper about the project. And it seems to be having the desired effect: Pebble Beach Golf Links recently agreed to conduct 200 underwater cleanups a year for at least five years. “It was really exciting to see that they’ve taken those first steps, and hopefully they become a leader in the golf industry,” Weber, now 19, told Reuters, “showing other courses how to run their sustainability programs.”