Shadow of the Shark by Mary Pope Osborne

Jack and Annie land on a beach in Mexico, where their relaxing visit quickly turns into a race against time when a shark is spotted near the shore. To fulfill their mission, they must learn about the ocean and help others stay safe. Along the way, they encounter sea turtles, dolphins, and underwater wonders. The story combines marine education with an exciting plot twist. It’s a sunny adventure with a splash of danger and ocean magic.