Surface Pressure by Adrian J. Smith

A mermaid. A human. Can they break the surface pressure?
Soulara never wanted to be queen. As the rightful heir, Soulara resists expectations in search of her own path. With a knack for technology and an insatiable curiosity, she explores the deep soundings and the surface. What she finds will kill everything in the ocean.
Autumn Walton is nothing more than a grunt. She joined the military to escape her family and found herself on a planet, mining water, in hopes to save her people. On a day of respite, she meets a strange creature in the water—a creature she’d been told was nothing more than a myth. Now she knows if the mining continues, she’ll kill the woman she loves.
From two different worlds, can Autumn and Soulara work together to save the ocean? Or will their forbidden relationship snap under the pressure of duty?