Skirmishes by Kristine Kathryn Rusch
Skirmishes (2013) is the fourth novel in Kristine Kathryn Rusch’s DIVING universe. It begins a month after the events in Boneyards which, of course, you’ll want to read first. Skirmishes has a structure similar to Boneyards – there are two main plotlines (one starring Boss and the other starring Coop) and one of them jumps around in time.
In Boss’s plotline, she’s trying to get into the Boneyard which is,