Millie and Storm

"Hidden deep beneath the waves is Mermaid Academy, a magical school where mermaids are paired with their very own dolphin and must discover their unique mermaid magic, with plenty of adventure along the way! Millie loves solving mysteries! So when the magical Sea Sphinx sets her a difficult riddle, Millie can't wait to get started. But when her puzzle solving leads her straight into a Mal Mer trap, she needs Storm and her friends to dive to the rescue!"--Amazon.com.