Cuttlefish will go to great lengths to deter competitors, displaying different patterns on each half of their bodies. Re the footage above:
[Researcher Culum Brown] saw a male cuttlefish swimming between a female and a rival male, and displaying different messages to both of them. On his left half, the one the female could see, he flashed zebra-stripe courtship colours to advertise his interest. But on his right half, facing the rival male, he flashed the mottled colours of a female. As far as the competitor was concerned, he was swimming next to two females, oblivious to the act of cross-dressing/seduction going on right next to him. The cheater, meanwhile, prospers.
An obvious human equivalent: straight men going to gay bars to pick up the female friends of gays. Losing homophobia is a great mating strategy.
Update from a smarty-pants reader:
Cuttlefish aren't fish – they're cephalopods, which are in the mollusk phylum. (We are more fishy than they are.) Obviously, "fish" is a part of their common names, but the title of your post should not have called them fish.