The structure of Africa's southernmost coral communities, which grow on submerged fossil dune and beachrock systems and do not form true coral reefs, was quantitatively investigated by means of line transects and phototransects. None of the typical geomorphological reef-zones such as lagoons, reef crests or reef slopes were developed. A uniform community structure, differentiated only into two major community-types with three subcommunities, was found, Shallow reefs were dominated by alcyonaceans and differed from scleractinian dominated deep reefs. A high proportion of alcyonaceans was found in shallow communities (40–60%). Subcommunities, which were found on most reefs, were an alcyonacean dominated "reef-top" community in areas of low sedimentation, dominated by the genera Sinularia and Lobophytum, and a scleractinian dominated "gully" community (predominantly Montipora and Faviidae), in areas of high sedimentation. A deep sponge-dominated subcommunity existed on the deepest outcrops. The lower limit for most coral growth was between 35 and 40 m.