That alone makes it unusual. Holy wells are typically inland features, associated with fresh water and quiet pilgrimage; this one occupies a liminal, tidal position beside a quay, its sanctity and its saltwater surroundings existing in easy contradiction.

The well is known locally as Tobar Cholmcille, meaning the well of Saint Colmcille, one of the most widely venerated early Christian saints in Ireland and Scotland. The name on the Ordnance Survey maps is something else entirely: Tobergallankillave, a contortion so severe that the travel writer Tim Robinson, in his 1985 work on Connemara, suggested it had been taken down from an islander with a bad cold. It is a small, wry reminder of how much was lost, misheard, or simply mangled in the process of mapping Irish-speaking places through the medium of English. The well itself is a natural feature rather than a constructed one, a smooth cylindrical pothole roughly sixty centimetres across and sixty centimetres deep, worn by water into the rock. Its precise location has also drifted on paper: the physical well sits around a hundred metres south-east of where the OS six-inch maps place it.

The pothole lies close to the quay on the island's eastern shore, which gives a visitor something to orient by. The tidal position means the well may be submerged or surrounded by seaweed depending on when you arrive, so timing the visit around low water makes it considerably easier to locate and examine.