Quiet wakefulness. Serenity, alive, in touch with her passengers, moved with them as if she had a circadian rhythm of its own. When she was calm, River could feel the ship as it moved through her daily rhythms, just like any person: wake, live, go about her day, tire, sleep. And when she was calm, River latched herself to that rhythm, living it, breathing it, sinking inside her.
-- The Passenger Book 2: Chameleon (part 17) by serafina20