Currents Converged. The Isla Emerged Series

Peril. War. Power. Isla has been queen for five years, but time has not made ruling any easier. It also hasn't erased the guilt she feels over her part in the pain her people suffered. But as queen, she has more important things to worry about than her feelings and some gruesome flashbacks. She must atone for her sins and help the merfolk of the Southern Pacific heal from the wounds her mistakes left behind. Unfortunately, achieving that will be harder than she ever imagined.
Theo, a prince from a faraway kingdom, arrives with a harrowing warning that a new tyrant has emerged and old enemies have risen from the grave-and they're working together to terrorize the mer world. Now, Isla must gather her friends, rally her army, and battle her own demons in order to protect her people and put an end to her enemies before it's too late. War is coming. The survival of the seas rests on Isla's shoulders. And victory is the only option she has. Currents Converged is the final book in the Isla Emerged Trilogy.