#1 New York Times bestseller and Newbery medalist Linda Sue Park starring a young snorkeling enthusiast who draws inspiration for fighting climate change from interacting with her pesty little brother.

Inspired by her own experience, beloved author Linda Sue Park tells the story of a girl learning how to impact a cause she cares about while navigating the ups and downs of a sibling relationship and turning disappointment into opportunity.

Gracie loves snorkeling! She loves it so much, she convinces her parents to let her plan a family vacation to Roatán, Honduras, where they can all snorkel together. She even makes a new friend there. Now, if only her irritating little brother would leave her alone, everything would be perfect. Then Gracie hurts her leg, and all her carefully made plans start to come apart. Worse still, she learns the reef itself is in serious danger. Gracie wants to help the reef . . . but she's just a kid. What can she do to make a difference? Fortunately, her new friend has a few ideas!