An appealing heroine, zippy prose and a preposterous plot make entertainment for young teens. Jade, nearly 14 and a bit on the chunky side, finally experiences her first period—but also discovers that she’s part mermaid when she gets too comfy in her bath. Dad knew that Jade’s mom was a mermaid, and no one understands how Mom could have drowned last year—until Jade discovers that she is being held hostage by an evil mer-couple in the local lake. Boudreau’s characterizations ring nicely true, as Jade juggles her fight to free her mom with her own friendships and the unlikely interest of a popular, handsome boy. A nice sprinkling of wry humor keeps spirits up, but even for a fantasy, the plot conjures the term “eye rolling.” A good fantasy makes readers believe; this one has enough dei ex machinae to populate Mount Olympus. However, the author keeps suspense high and her prose moving while tapping straight into young teens’ angst about friends, enemies and boys. A talented writer aims too low but nevertheless produces light fun. (Fantasy. 10-14)