Easy to miss and unlikely to feature on any itinerary, it is what remains of a fish weir, a structure designed to trap fish as the tide recedes. Post-and-wattle or post-alignment weirs of this kind work on a straightforward principle: stakes are driven into the riverbed or estuary floor, often strung with wicker panels or netting, creating a fixed barrier that channels fish into a confined space at low water. The posts here run east to west across roughly four to five metres of creek.

The weir has been dated to the post-medieval period, placing it broadly in the centuries after 1600, when the Shannon estuary was well trafficked and communities along its banks depended heavily on its fish. The site was recorded in February 1997 by Aidan O'Sullivan, whose survey of intertidal archaeology along the Shannon documented numerous such features. Post alignments of this kind are rarely spectacular to look at, a few dark stumps protruding from grey mud, but they carry a direct material connection to the working lives of people who fished these waters when Bunratty Castle was already an old building and the estuary was still a working highway.