Shallow subtidal, under-rock invertebrate communities at Lough Hyne Marine Reserve, County Cork, Ireland have changed significantly in recent years. Aside from the well-documented mass mortality of the purple sea urchin Paracentrotus lividus over a decade ago, noteworthy faunal differences in the period of 2014 to 2017 at the shallow subtidal monitoring sites included the proliferation of spiny starfish and ascidians and the increase and then demise of a previously undetected serpulid polychaete Metavermilia multicristata and the uncommon, inarticulate brachiopod Novocrania anomala. Two new records include the appearance of the calcareous sponge Clathrina rubra and echiuran Thalassema thalassema. Based on retrospective analyses of digital photographs, the dynamics of M. multicristata and N. anomala were elucidated. Some faunal differences may have been due to changes in current patterns and, hence, larval recruitment patterns. In contrast to such taxa, the newly reported sponge-dwelling barnacle Acasta spongites and flatworm Procerodes littoralis were undoubtedly overlooked previously due to their small size and cryptic habitat. These records are timely reminders that even well-studied shores may have insufficiently recorded species.