The well on Fínis, a small island in Galway Bay, behaves quite differently. Known locally as Tobar Cholmcille, it lies below the high-water mark on the sandy eastern shore, cut into the granite bedrock itself. The sea covers it for much of the day. Only at low tide does it become visible, a shallow oval depression roughly the size of a dinner plate and a quarter of a metre deep, filled with water where the rock dips just enough to hold it.

The well is dedicated to Saint Colmcille, one of the most widely venerated figures in early Irish Christianity, associated with dozens of sacred sites across Ireland and Scotland. Local tradition, recorded by the cartographer and writer Tim Robinson, described the well as being shaped like a bowl, with a clochar around it. A clochar, in this context, is a cairn or small stone monument, sometimes called a leacht, of the kind often used as a focus for devotional circuits or patterns at holy sites. There was also said to be a path leading down to it. When surveyors visited, however, no trace of the clochar or the pathway remained. Whether they were dismantled, submerged, or simply worn away over time is not recorded.

The well is accessible only during low tide, which makes any visit a matter of timing and attentiveness rather than casual tourism. It sits on the eastern shore of Fínis, and what a visitor would find is modest by any measure: a small hollow in grey granite, easily missed, with nothing to announce its significance except the knowledge of what it once was to the people who made the crossing to reach it.