Fathom: Killian's Tide #1

Synopsis

After the undersea city of Marielle is accidentally destroyed by a hydrogen bomb during nuclear testing, the council of the Blue convenes to discuss how to handle the problematic humans of the surface world. When the council advocates leniency rather than vengeance, Killian joins a band of young dissidents led by his brother Sear in order to make the humans pay for what they have done. The dissidents manage to blow up a human power plant but Killian barely escapes with his life when things don't go according to plan.