Yet this is one of the more peculiar features of the structure beside the Cong river in County Mayo, a roofless single-storey building known traditionally as the Monk's Fishing House, sitting on a stone platform built over the water itself.

The building is small, roughly three and a half metres by three metres internally, constructed of mortared stone with a pointed doorway in its east gable wall. A semicircular fireplace occupies the west gable, with a rectangular chimney above it, and two windows look out over the river to the north. The overall impression is of somewhere designed for occupation rather than purely for storage or ceremony. The exact date of construction is uncertain. The architectural historian Harold Leask, writing in 1941, proposed that it may have functioned not as a fishing station in any simple sense but as a watchhouse for the abbey's fishing weirs; weirs being low barriers built across a river to trap fish, requiring some degree of monitoring and maintenance. The abbey in question is the Augustinian house at Cong, which lies roughly ninety metres to the east and was one of the more significant monastic foundations in Connacht. The combination of a hearthside seat, windows trained on the water, and a hole in the floor through which a line or a net might pass suggests a place where a monk could wait, warm, and watch the river do its work.