That alone sets it apart from the thousands of holy wells scattered across Ireland, most of which occupy dry land and are tended with offerings, rags, and rosary beads. This one belongs, at least part of the time, to the tide.

The well itself is a pothole, roughly 0.3 metres across, described as fine, smooth, deep, and round, worn into the rock by natural geological forces over a very long period. Beside it, on the same rock outcrop to the east, are the remains of a small cairn, a modest pile of stones that would once have marked the site as significant. Locally, the well is associated with St Columcille, the sixth-century monk born in Donegal who founded the monastery on Iona and whose cult spread widely across Ireland and Scotland. Columcille, also known as Colmcille or Columba, accumulated a remarkable number of dedications across the west of Ireland, many of them at marginal or liminal places, shores, cliffs, and tidal zones where the boundary between one world and another felt genuinely uncertain.

Because the site sits below the high-water mark, access depends entirely on the tide, and the cairn beside it may be partially disturbed or difficult to make out depending on conditions. The pothole itself, smoothed by both water and time, is the surest thing to look for on the exposed rock surface at the bay's northern edge.