The structure is easy to overlook entirely, and that is precisely what makes it worth attention. It is not a ruin in any dramatic sense, but rather a functional ghost, the faint outline of a working technology that would have fed people along this estuary for generations.

Recorded in July 2000 and described by archaeologist Aidan O'Sullivan, the structure takes the form of a U-shaped arrangement of posts set into the creek bank, oriented roughly north to south. It measures around 3.6 metres in length, with a mouth approximately 1.8 metres wide that narrows to about 80 centimetres at its southern end. Leading into this enclosure from the northwest is a short post-and-wattle fence, roughly 2 metres long. Post-and-wattle construction involves driving upright stakes into the ground and weaving flexible branches or rods between them, a technique used across early medieval Ireland for everything from building walls to managing water. Here, the fence would have guided fish into the narrowing trap as the tide receded, leaving them stranded. O'Sullivan noted its similarity to a structure at Bunratty, known as Bunratty 4, suggesting this was a recognisable form along the Shannon. Whether the Bush Island example is genuinely medieval remains a question, but the comparison to other dated estuary sites gives the possibility real weight.