In the River Suir near Greenan in County Waterford, a low ridge of dry-stone walling breaks the surface of the water. It is easy to miss, and the first Ordnance Survey map of the 1840s recorded it as a small island, the exposed stones giving little indication that they were once part of a working fish weir, a barrier built across a river to trap or direct fish, often channelling them into baskets or nets anchored at gaps in the structure.

The Civil Survey of 1652 to 1654 recorded three weirs on the River Suir, referred to in that document as the River of Sewer, lying between the lands of Abyneslewnaght, Gryenane, and Kilnamacke in the barony of Glaunyhiry. The survey noted that these weirs had, in 1640, been the property of the Cistercian monastery of Inislounaght, whose remains stand approximately 200 metres to the north-west of where the surviving stonework lies today. By that point the weirs had passed into the hands of Patrick Goegh of Kilmanahan. The Cistercians, whose religious rule placed considerable emphasis on self-sufficiency, were historically prolific builders of fish weirs across Ireland and Britain, and a river as productive as the Suir would have been a significant resource for the monastic community. The surviving structure in the Suir is thought to be one of those three weirs, and it may originally have extended all the way across to the boundaries of Greenan and Kilmacomma on the opposite bank.