Not a natural outcrop that people happened to use, but a constructed or heavily modified place, linked to the mainland by a causeway of marl and peat, fitted out with floors woven from basketwork, divided by partitions of the same material, and equipped with hearths. The animal bones found throughout suggest sustained habitation rather than occasional visits. Shore Island belongs to a tradition of lake settlement found across Ireland in the form of crannogs, artificial or semi-artificial islands built up in shallow water to provide a defensible, controlled living space. What makes this site quietly unusual is the degree to which the construction extended into the water itself.

When the geologist G. H. Kinahan examined the island in the early 1860s, he recorded masses of stone arranged between and outside two semicircles of oak piles along the north-eastern shoreline and running from east to south. A further three circles of piles were visible about twenty metres to the south of the island in the lake itself. Excavations carried out on the eastern half of the island uncovered the basketwork floor and partitions, the hearths, and the accumulation of animal bone. Those oak piles along the shore were revisited in the late 1990s, when a diver identified them not simply as structural remnants of the island's perimeter, but as the remains of an artificially constructed small harbour or docking area. That finding reframes the whole site: this was not simply a place people lived on, but one they arrived at by boat through a purpose-built approach, the island functioning almost as a small, self-contained node on the lake.