The Chronicles of Acqueria: Blood Moon Treachery

At sixteen summers, Sentia is about to be joined for life to a man she does not love, while custom forbids her the one does. The two young men, submerigible pilots in the service of the rocky and shaky Acqueria, become rivals in pursuit of a lofty prize, for Sentia is the daughter of the Chief Elder. One of the young men would destroy his future for her, the other would destroy her for his future.