It is not the kind of discovery that makes headlines, but it raises questions that are difficult to dismiss. This well, sitting roughly 37.5 metres to the north-east of Bullock Castle on the Co. Dublin shoreline, was not simply a hole dug for water. It was enclosed within a small rectangular structure of uncertain purpose, capped with re-used dressed granite slabs, and at some point in its working life it received what may have been deliberate deposits, or simply the accumulated debris of a place that was used, abandoned, and eventually buried beneath a tiled floor.

The excavation, carried out by O'Brien in 1990 and referenced in an unpublished report (E000971), revealed the well to be a careful piece of construction. It was lined with granite stones and boulders, the gaps filled with granite spalls and a putty-like clay to help hold everything in place, and it descended 2.5 metres to a concave base about a metre in diameter. More intriguing still was the lead pipe found running upward from the base of the well as a bore, a simple pipe intended to channel water under pressure, though its outlet was never located within the excavated area. The rectangular structure enclosing the well measured at least 3.9 metres east to west and extended further south than the dig could follow, and its function remains unidentified. Above all of this, a floor of red and grey tiles laid in the 19th century had sealed the whole thing in place, preserving the organic layer and its small, strange contents below.

The site sits north-east of the junction of Harbour Road and Breffni Road in Bullock, a small harbour settlement that forms part of the broader Dalkey area south of Dún Laoghaire. Bullock Castle itself, a 12th-century Anglo-Norman tower house built to protect the local fishery, is a visible landmark nearby and gives a sense of how long this particular patch of shoreline has been in use. The well is not a visitor attraction in any formal sense, and there is nothing to see above ground today; the archaeology is the record of it. What makes it worth knowing about is precisely that combination of the practical and the unexplained, a workaday water source fitted with lead pipework, enclosed in a building nobody has yet identified, and harbouring, at its muddy base, the tooth of a pig.