After Preston buys tickets to go on a week-long mini-cruise, he passes them out to his friends. Everyone is ecstatic to get out of Gravity Falls for a week and spend some time bonding on a boat. But when the boat travels through a storm, tossing everyone overboard and killing the captain, they're forced to tough it out on an uncharted island in the middle of the ocean. Stranded with limited supplies and sanity, will the group survive until they're rescued, or will starvation and the urge to murder their island mates kill them off first?