We Shall Sing a Song Into the Deep by Andrew Kelly Stewart
When she was a small child, Remy was rescued from death by a chaplain who oversees the monks on a submarine called Leviathan. They carry the world’s last nuclear missile and their mission is to wait, protecting the missile, until God tells them it’s time to deploy it against the wicked Earth on judgement day.
Remy’s job is to sing in the choir of eunuchs, a crucial role that keeps up morale. Her voice will remain high because she’s a girl (a secret that only the chaplain knows),