I tried some of those, with mixed results. "Sitter" is short for "babysitter" (typically a very active occupation!) and "sittee" just sounds to me like a mispronunciation of "settee". *"Liee" is just terrible; "lier" invites confusion with "liar" except in compounds like "outlier". "Croucher" and "crouchee" both work IMD, the first with a more active implication (i.e. I'd be more likely to use it for someone waiting in ambush). "Drifter" is established in the language, but with a metaphorical meaning; I'd be apt to use "driftee" for someone literally adrift in the sea.