CV is a 1985 science fiction novel by Damon Knight. It is the first novel in the "Sea Venture Trilogy", and was followed by The Observers (1988) and A Reasonable World (1991). The name of the novel derives from "The Sea Venture" ("CV" for short), an enormous, ocean-going habitat. During one of its first trips, the Sea Venture takes on a parasite, an alien symbiont that can pass from one person to another, leaving them changed in subtle but consequential ways. The symbiont enforces something like rational behavior upon its victims, causing them to question their earlier beliefs and practices. At the end of the novel, the parasite is brought to the mainland; the subsequent novels in the trilogy explore the consequences as it begins to affect a large part of the human population.