The Bone Master

Kaii Haku has lived his whole life in the shadow of his cruel father's magic.
Rebelling against his father- the Bone Master- by drinking and sleeping around.
But when one of his best friends is kidnapped by pirates, Kaii embarks on a perilous rescue mission with two retired pleasure house workers, a shy teen bookworm, and a feisty girl from the pirate crew.
The journey will take Kaii and his allies far from Achten Tan, to a sea ruled by ships that travel on the backs of monsters.
For the first time in his life, he has the power to make a difference, but if he wields his emerging bone magic to save his friends, he risks losing himself and becoming like his father - a man who tried to kill him.

This is the second book in the Sands of Achten Tan series, but can be read as a standalone.
It contains a complete adventure and no cliffhangers.