Spike, being the undead, unbreathing jerk he is, will remain mostly chill this event. If needed he can keep some people from drowning but most of the time he'll sulk on a raft somewhere, whining that his cigarettes are too soggy to smoke. Totally open for plotting.
Reid is available, tho I have no plans for him. He'll be fine, hating his life, what else is new.
Chuck... was already kind of dragged out of the ocean as a corpse once and I'm so goddamn tempted to do it again. Someone tell me no. Very no. Much no.