Unjust Depths by Madiha N. Santana

Hundreds of meters beneath a turbulent, uninhabitable surface, where light barely reaches through the distortions of the water, the communist Labor Union of Ferris, Lyser and Solstice scratches out a living for its people in former penal colonies won in a revolution against the vast and mighty Imbrian Empire. With the Empire and the Republic of Alaize locked into war, the Union bides its time and builds its strength, hoping to be ready to defend itself when the Empire returns.

Under this vast ocean, the actions of a few will ripple farther afield than anyone would imagine. When the Empire enters an era of internal chaos, the Union sees its chance to finally steer the tide of history in their favor. To connect the disparate resistance movements awakening in the Empire into a revolutionary front, a young crew aboard an experimental ship will embark on a journey across thousands of kilometers of ocean, discovering unlikely allies, dangerous foes and a myriad truths about life under the vast, brilliant blue water that surrounds their entire world.