Gr 14 In this "Mermaids Rock" series installment, mermaid Kai thinks his biggest problem is training his turtle Tommy to do tricks for the Spring Fair pet talent show. Then his friend Marina's father goes missing on his trip to study walruses in the Arctic, and Kai joins her and the other members of the Save the Sea Creatures Club on an educational, and dangerous, adventure to rescue him. This latest entry works as a standalone, though new readers may find themselves referring to the book's illustrated character guide to keep track of the diverse cast. Youngsters will enjoy the world-building elements, such as descriptions of mermaid homes and magical inventions, all of which are buoyed by pleasant gray scale illustrations. There is a clear undercurrent addressing climate change amid mermaid magic, along with typical kid concerns like friends moving away and bullying. The group's shared dedication to sea creatures teaches readers about underwater life from the perspective of fictional full-time residents, while abundant educational resources at the back provide factual information about the novel's animals and setting. VERDICT An older chapter book that explores sea life and conservation from a fun, fantastical perspective that is rooted in facts. Recommended for young readers who can't get enough of mermaids and marine biology. Ashleigh Williams, School Library Journal