Cass has always loved the ocean. Though she lives with her eccentric mother in a rundown camper on a Floridian beach, the water has always seemed to be her first home. But between picking up her mother's missed shifts at the diner, navigating high school friend drama and boy trouble, and trying to fit in when her strangeness is obvious at a glance, Cass can't help but be a realist. Circumstances have forced her to mature before her time. But also . . . mermaids might actually be real?
After a late-night swim reveals more about herself than she ever could have imagined, Cass is set on a path that exposes ancient secrets and introduces mythical responsibilities. Protecting this new way of life comes with a high level of risk, even with the support of her mother. But with the normal stress of being a teen and the extra stress of being a mythical creature, familial bonds will be strained, and figures from her past might spell the end to Cass's life by the sea.