The Marrow Tide

In the crushing dark beneath humanity's drowned Earth, pilots called Vessel-Bearers wear the resurrected bodies of an ancient sea-born species to fight a relentless enemy that rises from the trench. Kael Doran is the finest Bearer alive, chasing glory only to keep his little sister safe topside — until the alien voice sleeping inside his own Vessel starts speaking back, and he realizes the war he's dying for may be the greatest lie ever sold to a drowning world.