Tales of a Sea Witch - Tales of the Sea, #1

No creature under the sea is born dark; some just lose themselves. Irsa's name was lost long ago to the obscurity of being labeled a villain. Born with enough magic to boil the ocean, all Irsa wants is a simple life with her best friend, Aislin. But when they discover their connection is more than just friendship, the pair must fight all odds to be together. Surviving the sea isn't easy, but Irsa has never known any different.
With Aislin by her side, she must face a wicked witch, defy a prince, and maybe gain all she ever wanted: a happily ever after. Tales of a Sea Witch is an origin story full of mermaids, and undersea magic for fans of Tithe by Holly Black, and Wicked by Gregory Maguire.??