Echoes of the Tide by Emma Hamm

Ace has spent her entire life hiding who she is. First, it was from friends and family who didn’t know she was stealing from the rich. Then it was hiding her true self in a prison city under the water. The worst was hiding herself from new friends who helped her destroy Alpha. What she didn’t know, was that decision would force her to come into the light.
Maketes has always been the jokester. No one takes him seriously, and if they do, it’s only because he was born violent. But then he starts talking with a human through droids, and he finds a kindred spirit in them. When he’s given an opportunity to find out who this human really is, he takes it.
But what he finds in that prison city is not just the person he was friends with. He finds a villainous group of people who wish to use him to their advantage, and a woman who captivates his entire soul.
Together, they travel throughout the remains of Gamma, a city long forgotten. And while they search for a key that will change how they see the entire world underneath the ocean, they find themselves growing closer. Soon enough, they realize that perhaps hiding their entire lives has prevented them from experiencing the greatest part of life.
Love.