fth grader Marena Montoya is learning how marine mammals talk to each other. But her bigger challenge is learning how to communicate with her new study partner, Samuel, as sea mammal rescues--and their own lives--will depend on it.

When Marena Montoya and her new study partner, Samuel, embark on a shared mission, they get off to a shaky start. They need to research how whales and dolphins communicate, but they barely know how to talk to each other. Luckily, Marena's OceanX mentor, Dr. Anna Knowles, is a marine mammal expert and an excellent coach.

A baby otter and a dolphin need Marena and Samuel's help, but when the team investigates an underwater noise issue, they become the ones in need of rescue. Trapped and in trouble, can Marena and Samuel escape on their own? Or will they need a little help from a sea mammal friend?

MEET THE OCEAN EXPLORERS: Curiosity and perseverance get fifth-grade junior science journalist Marena and her study partner, Samuel, in and out of exciting (and dangerous!) situations as they use critical thinking and sound science to solve an underwater mystery.

MENTORED BY OCEANX: Marena is mentored by Dr. Anna Knowles, whose character is inspired by the real-life scientists of the world-renowned OceanX project.

REAL SCIENCE: Each mystery is based on actual oceanic science research and discoveries and is filled with fascinating facts about the ocean world.

MIDDLE-GRADE MILESTONES: Eleven-year-old Marena and her study partner Samuel need to work together--whether they like it or not. Slowly, and with the encouragement of Marena's OceanX mentor, the pair learn about the importance of communication--and trust.

COLLECT THE SERIES: Mystery at the Aquarium and Danger in the Deep Sea also available!