The author's sampling on western coast Southern Baikal in 16 km northeast from the source of the Angara River was a material for work. A quantitative survey was done monthly during a period from April 1989 to August 1990. Benthic samples selected on the water edge, 1 and 2 meters (m) higher of it towards the land and through each meter lower of the water edge during 20 m. Abiotic factors affecting zoobenthos have been recorded. The periods, differing on character changes of a beach, have been allocated. The minimum index of benthos are marked during the maximum hydrodynamic influence, the maximum index - during the minimum hydrodynamic activity - in the subice period. 30 species of benthic animals have been found at the beach zone (water edge and underwater edge zone). They belong to Turbellaria, Hirudinea, Oligochaeta, Polychaeta, Bathynellacea, Amphipoda, Isopoda, Plecoptera, Trichoptera, Chironomidae, Mollusca, Collembola, Diptera larvae, Coleoptera larvae, and Acarina. All animals found in a beach fall into three groups: occasional species, migrating species, and obligatory beach dwellers. Obligatory beach dwellers consist of two species complexes: amphybionts and hydrobionts. This is peculiar for marine supralittoral. Five macrozoobethic communities were found: 3 communities with dominant amphipods, 2 with dominant oligochaets. Predominance of this or that zoobenthic species is determined by the size of substratum pores. Communities are formed during periods of weak hydrodynamic stress (May - August) in a beach zone with appropriate grounds. While increasing of a hydrodynamic effect on the beaches (September - December), the communities migrate to the zones of weak hydrodynamic stress, and they are missing at a water edge. Biology of endemic amphipod EULIMNOGAMMARUS CYANEUS has been investigated. This species is an attractive model for micro-evolutionary studies since it inhabits a very narrow zone a few meters wide, and 2 000 kilometers long.