This reports on a project that combined evidence gleaned from aerial photographs, place-names, interviews, topography, LIDAR data, and sonar bathymetry to locate stone tidal fish weirs in the Molene Archipelago. The results were verified by diver and pedestrian visual surveys. Models of Holocene sea-level change allowed a group of possibly Late Mesolithic-Early Neolithic weirs to be recognized, with a second group broadly dated to the later Neolithic-Early Bronze Age. The construction of these long megalithic structures is compared to the funerary monuments for which the Molene Archipelago is well known, in terms of technique, cost, and societal organization.