At its centre is a small island, and from that island two projections extend eastward and westward into the water. This is not the layout of a working pond or a simple ornamental feature; it is the distinctive geometry of a decoy pond, a type of wildfowl trap common on large estates from the seventeenth century onward. The design typically relied on curved, netted channels called pipes that fanned out from a central point, drawing ducks inward with the help of trained dogs and the natural curiosity of waterfowl. The circular form and the projecting arms at Ballynacronny are consistent with exactly this kind of installation.

The pond appears on both the first edition and current edition Ordnance Survey six-inch maps, suggesting it has retained its shape over a considerable period. Its likely connection to Annfield House places it within the managed landscape of a landed estate, where the maintenance of a decoy would have supplied the household with wildfowl and offered a form of organised sport for its occupants. A separate circular landscape feature lies about 200 metres to the west, hinting that the designed grounds around Annfield were more elaborate than what survives today.