A sea rancher was a type of rancher who practiced ranching in the open sea.

Ruth Bonaventure, one of the women Harry Mudd had recruited for wiving settlers on Ophiucus III, came from a pelagic planet, populated by sea ranchers, all of whom lacked the necessary requirements for being a potential husband. (TOS: "Mudd's Women")

In the final draft script of "Mudd's Women", these laborers were instead called "sea farmers."