Together they measure little more than half a metre across, yet they represent one of the most quietly ingenious pieces of engineering on the island: a purpose-built water supply for monks who had almost none to spare.

The two basins sit side by side on a low rock shelf close to the western corner of the oratory, the small stone building that forms the focus of what researchers have called a hermitage separate from the main monastic complex. A channel running beneath the north-western wall of the oratory feeds them, along with two grooves cut into the rock-face above, directing whatever rain fell on that exposed Atlantic outcrop down into the hollows. The north-eastern basin, roughly 0.5 metres by 0.36 metres and 0.12 metres deep, has a circular depression worn or cut into its base; when it fills, water overflows along a small channel into the second basin to the south-west, which is marginally larger and slightly deeper. The whole system is interconnected, cascading from one basin to the next. The basins remained unrecorded until Grellan Rourke cleared sea campion from around the north wall of the oratory, revealing beneath the plants a flagged path and, at its western end, the steps that lead down to them. Horn, White Marshall, and Rourke, writing in 1990, noted that both the shape and location of the basins made their function unmistakable: they were there to collect water, full stop.

What makes the discovery quietly arresting is less the scale of the engineering than the patience it implies. The monks who occupied this southern hermitage, almost certainly a place of more severe withdrawal even by the standards of Skellig, cut their water supply by hand out of bare rock, groove by groove, in a spot so obscured by vegetation that it went unnoticed by modern visitors for generations. The basins are not large enough to sustain many people for long; they are the water provision of someone living alone, or nearly so, on the edge of the known world.