Heart of the Moon Goddess by Joline Lim (paperback)

A girl born with the power of the moon. A prince gifted with the radiance of the sun. And the rise of the sea king, the Bakunawa. Luna has been haunted by the same dream for weeks-tortured by flames in an arena, accused of witchcraft, and saved by a mysterious figure. Raised in the House of Wives, she was groomed to become a future bride for royals and noblemen. But Luna harbors a secret: her heart glows like the moon. During a sea voyage with the prince, Luna falls overboard and discovers an underwater cave. There, she encounters a man in chains who bears a striking resemblance to her dream's savior. As Luna unravels the mystery of her dreams and her glowing heart, she must confront a destiny that could change everything.