This one on the South Strand at Rush, County Dublin, carries none of those things, and yet it carries something arguably more interesting: a warning to strangers. Known as Tober Caillin, or Tubber Colleen, it survives today as little more than a slight pooling of water on a rocky foreshore, a natural spring seeping out at the base of a cliff, easy to walk past without a second glance. The designation "holy well" is, in this case, something of a loose one. Folklorist Caoimhín Ó Danachair, writing in 1958, noted bluntly that there is no tradition of devotion attached to the site.

A field visit recorded by Henry A. Wheeler in May 1975 described it as a small stream flowing down onto a rocky strand, with no regular pool but one or two natural hollows in the rock. Wheeler noted a fragment of wall just above the high tide mark that may have been built to collect the water, though its precise age and purpose are unclear. The well's association with St Mac Cuilín of the nearby monastery at Lusk has been suggested by name alone; no saint is formally connected to it in any recorded tradition. What was collected instead came from the Rush Schools' Folklore Collection, part of the great 1930s national survey in which schoolchildren recorded local knowledge from older community members. The tradition they preserved is quietly specific: if a stranger drinks from this well, it is said, they will make their home in Rush.

Finding Tober Caillin requires some patience. It sits on the rocky foreshore of the South Strand, at the base of a low cliff, and at anything above low tide the water may be barely distinguishable from the surrounding rock pools. The fragment of wall Wheeler mentioned is the most useful marker, positioned just above the high tide line. It is the kind of place best visited on a calm day when the tide is out, when the foreshore is accessible and the spring has a chance to show itself. There is no signage, no pattern day, and no votive offerings left by passing pilgrims. Whether the folklore surrounding it reflects a very old tradition or simply a piece of local wit directed at the susceptible and thirsty is, at this point, impossible to say.