This is book number 2 in the Vicious Deep series.
Second in a YA fantasy series from the author of Labyrinth Lost, Tristan is pulled between duty and love as he vies for the Sea Court throne--and a betrayal will put all he loves in danger.
In the quest for the Sea Court throne, Tristan has already watched one good friend die. Now he must lead the rest on a dangerous voyage in search of the trident that will make him king. But while Tristan chases his destiny, the dark forces raging against him are getting stronger, and the sea witch of his nightmares is getting closer.
Battling pirates, sea dragons, and mutant creatures of the deep, Tristan needs his friends' support. But they each have their secrets, and a betrayal will force Tristan to choose between loyalty and ambition, friendship and love. In the race for a throne, all's fair in the savage blue.
The Vicious Deep Series:
The Vicious Deep (Book 1)
The Savage Blue (Book 2)
The Vast and Brutal Sea (Book 3)