It is only visible at the lowest tides, which gives it an intermittent, almost ghostly presence in the landscape, a structure that appears and disappears according to the rhythm of the water rather than the convenience of the visitor.

Fish weirs of this type work by channelling fish into an enclosed trap as the tide retreats. This example, which dates to the post-medieval period, takes a V-shaped or U-shaped form, its two fences angled to funnel whatever swam in with the flood tide and could not find its way out again. The larger of the two arms, the flood fence, runs roughly west-northwest to east-southeast and extends some 45 metres in exposed length; the shore fence, oriented northwest to southeast, runs to about 30 metres. Both are constructed in the tidal clays to the south-west of Quay Island. The structure was recorded by Aidan O'Sullivan in February 1997, and his survey documented it as one of a number of intertidal features along this stretch of the Shannon, a coastline that preserves traces of fishing practices that otherwise left little mark on the historical record.