 The river originally spilled into the Bass Strait, south of the town of Port Fairy, through a series of narrow channels that led westward from the site of the present-day mouth.At that stage, the southern outlet of the Moyne, the Back Passage, was narrow and the opening to the sea was often too rough for boats to leave or enter the port; the main eastern outlet was blocked by a shallow sand bar.These navigational impediments led to the construction of a jetty from Flagstaff Hill and a boulder wall breakwater between Griffiths Island and Rabbit Island.