The Chainbreakers

In this action-packed fantasy, thirteen-year-old Violet Moon must rescue her father and save her enchanted underwater world—perfect for fans of The Marvellers and Tristan Strong series.
All Violet Moon has ever wanted is to be a Reaper captain like her father. Born on the Tides of the Lost, a magical world beneath the waves of the Atlantic Ocean, Violet has spent her life at her father's side rescuing souls lost in the water.
But when a rescue mission turns to disaster after the arrival of the dreaded Children of the Shark, weaponized ghost-sharks who steal the souls for themselves, her father is seized and pulled down into the darkness of the Depths. With no choice for Violet but to inherit the captain's powers and helm the ship as the next in line, it'll be up to her to save her father—if he even still lives—and stop the Children of the Shark before they devour the world.
"A fantastical, mind-blowing adventure. . . Violet and her friends don't just smash barriers; they'll win over your heart, too." —Mark Oshiro, #1 New York Times–bestselling co-author of The Sun and the Star