Breakwater

"My name is Larkspur, and I am an Elemental."
My people use the power of the earth to sustain life and defy our enemies. I should be at my father's side as a royal princess. But as a half-breed, bastard child, that isn't going to happen.
As an Ender, one of my father's Elite guards, it's my job to do as I'm told. When my older sister is sent as an ambassador to the realm of the water elementals--the Deep--I have no choice but to accompany her as her bodyguard.
With the death of the water elemental's King, a deadly battle for the throne begins; a battle we are forced to choose sides in.
There are only a few things I know for sure. The ocean may be beautiful, but lurking in its depths are monsters to fear, the water I tread is teaming with danger and I am on my own.
With no one to help, and no one to trust, I have to find a way to keep my sister safe, and stop a civil war.
But the secrets within the Deep are far darker than any of us realized.
Welcome . . . welcome to the Deep.

From the WSJ and USA Today Bestselling Rylee Adamson World, The Elemental series is the perfect introduction point for new fans.

Rylee Adamson Series (Completed Series)
Elementally Priceless (novella)
Tracking Magic (short)Alex (short)
PricelessImmuneRaising InnocenceShadowed ThreadsBlind Salvage
TrackerGuardian (novella)
Veiled Threat
WoundedStitched (novella)
Rising DarknessBlood of the Lost

Rylee Adamson Epilogues (Completed Series)
RYLEE
LIAMPAMELALYNCHPIN

The Elemental Series (Completed Series)
Recurve
Breakwater
Firestorm
WindburnRootboundAsh
Destroyer
Peta (Novella)

The Questing Witch Series (Completed Series)
Aimless Witch
Caravan WitchMaze WitchElemental Witch