Race to the Bottom of the Sea by Lindsay Eagar (review)

Eleven-year-old Fidelia Quail is an inventor and a scientist in her own right, not so much following in her famous marine scientist parents' footsteps as walking alongside them. However, her miscalculation while tracking her own desire for scientific glory inadvertently leads to her parents' death, and it would have meant life on the mainland with her landlocked aunt were she not kidnapped by a fearsome pirate named Merrick the Monstrous. He wants her to invent a device that will enable him to retrieve his treasure, lost on the ocean floor and rendered inaccessible by a poisonous plant surrounding it. As their journey progresses, Fidelia realizes that Merrick has already been fatally afflicted with the plant's deadly pollen; he is dying, and their quest is therefore about something far more precious to him than treasure he won't be able to spend. She also discovers that the loyalty of his crew is well deserved, while the enmity of his enemy, Admiral Bridgewater, is petty and morally ambivalent. Although the chief danger they face, the Undertow, is ill defined, the rejigging of Fidelia's emotional compass is sensitively and accessibly handled in the midst of her harrowing adventures on a dodgy craft. Ultimately, Fidelia's problem-solving skills as well as her courage and ambition mark her out as a worthy hero for budding scientists and armchair adventurers.