TodHunter Moon, Book 1: PathFinder

Tod is 12 and finally old enough to hear the secret of her people, the PathFinders. At a special dawn ceremony, her father reveals that their ancestors were renowned for navigating something called the Ancient Ways, paths they no longer remember. Because of their skills, they were even sent to the stars. And, even crazier, many of the PathFinders today could still have gills like their ancestors who traveled in fluid through space. This is a lot for Tod to take in, and she has little time to process it before her father goes missing from his fishing boat one day. He leaves a note behind telling Tod yet more secrets. Her long-deceased mother had magical abilities and wanted her to study magic. Tod hops on a ship to meet Extraordinary Wizard Septimus Heap, not knowing that her village is in serious danger. Fires burn down most of the houses and most of the villagers go missing at the hands of strange nocturnal snake-like creatures called garmin. But Tod still has a chance to help them when the garmin start abducting people near the Magical Tower and Septimus finds out they're sneaking around through the Ancient Ways. The kidnapped will need Tod's help as a Pathfinder to navigate through the labyrinth of tunnels and save them on time.