Aquatic

Lilly is the daughter of one of the smartest American scientists. Her dad, Hunter Peterson, has invented a vessel that can explore the deepest depths of the Pacific. So, they launch an expedition to the bottom of the Mariana Trench and are shot down by an underwater society that reside in the underwater city of Cascade. There, Lilly and a boy from the city, Salim, become friends within all the confusion of people from "above."