Its exact location is unknown, absorbed long ago into the urban development that remade the waterfront, but the well survives in fragmentary documentary form, conjured from two brief references separated by two years and more than three centuries of subsequent silence.

The primary account comes from Roderic O'Flaherty, the Connacht antiquarian and historian who, writing in 1684, described the ruins of the Earl's house, known in Irish as Clogh-an-hiarla, meaning the earl's stone, standing near the quay. Beside those ruins, he noted, was a well dedicated to St Brendan, and that the feast day of the saint, the sixteenth of May, was customarily observed as a holy day by the residents of Quay Street. The earl in question was the Red Earl, Richard de Burgh, the powerful Anglo-Norman magnate whose great hall in Galway was one of the most significant medieval structures in the west of Ireland. The association of a sacred well with such a prominent secular site is not unusual; holy wells in Ireland were frequently embedded within the social and physical landscape of a settlement rather than set apart from it. A property lease drawn up in 1686, just two years after O'Flaherty wrote, refers to something called the Earl's Well, which may be the same feature under a different name, one that had by then shed its religious identity in favour of a more practical, proprietary one. The likely area, based on both references, is somewhere in the vicinity of the present Custom House on the Galway quays.