Α semi-buried underwater beachrock exposure, in the west coast of Thassos Island (N Greece), has been investigated due to coastal erosion phenomena. The partial removal of the beachrock’s outcrop by locals incurred rapid regression of the beach, while the protected by the formation coast, remained stable during the same time interval. The use of the Bruun Rule as a contributor in the quantification of the marine transgression in the study area showed a participation of the sea-level rise to the beach erosion equal to 7% of the total erosion at minimum. Several other factors, which are related to the unique dynamic conditions at the eroded coastline, might have contributed to augmented erosion values.