"Sex for fish."
That unlikely phrase is used in some lakefront communities in sub-Saharan Africa and other parts of the world where men catch the fish and women sell the catch to local customers.
In Malawi, for instance, a woman may take a fisherman's catch and promise to pay him once she's made her sales. Only she might have trouble selling all the fish. So she might pay off what she owes for the fish by engaging in a sexual encounter.