Castle Well at Ballinesker appears on the Ordnance Survey six-inch maps of both 1839 and 1924, labelled identically in each edition, which suggests it was a recognised landmark across that interval. Today, the land has been drained and improved for grazing, and the well has effectively vanished into the field.

The site lies at the foot of an east-facing slope of an esker, roughly 120 metres from the shore to the south-east. An esker is a long, winding ridge of gravel and sand deposited by meltwater streams flowing beneath a glacier during the last ice age; they are common across the Irish midlands but appear near the coast too, and their slopes often collect and channel groundwater in ways that make them natural locations for wells. The name Castle Well implies some association with a nearby fortification, though no detail of what that structure may have been survives in what is recorded about the site itself. The persistence of the name through both the mid-nineteenth and early twentieth century maps at least confirms it was meaningful to local communities across that period, even if the physical source has since been buried beneath land improvement works.