* FirstInstallmentWins: The second and third movies genuinely lack the charm of the original.
* HoYay: Between David and Mark. You'd think there was something there that David didn't want Kay to know about...
* IAmNotShazam: the monster is never actually referred to as "Creature from the Black Lagoon". He's called "the creature" a few times, but never the full title. His official name, especially in the second movie, is "Gill Man".
* NightmareRetardant: Posters for the film developed an odd tendency to give Gill Man a pair of clownish red lips.
* StrawmanHasAPoint: Mark may be Jerkass, but if they'd listened to him, they'd have wound up a lot better: If they'd killed the monster (who they knew had killed at least 4 people previously, at least 2 without provocation) they'd have been fine. If they'd have left when he wanted to, rather than taking pictures of the cave than the monster probably wouldn't have broken out. And if he hadn't gone underwater after David, than David would have almost certainly died.