This text treats rocky, sandy and muddy shores worldwide. It describes the major factors which determine the biological make-up of rocky shores, sandy beaches and mudflats. Patterns of distribution of intertidal organisms are described worldwide and the dynamic processes that underlie these patterns are discussed in detail, especially predation, competition and disturbance. This is carried out in the framework of the four main environmental gradients: shore height, wave exposure, particle size and salinity, thereby enabling all types of shore to be treated in a comparative way. The authors assess the ecological consequences of human activity on the shore, particularly the effects of exploitation for food, organic enrichment and oil pollution, and the consequences of sea-level rise due to global warming. Techniques for investigation of the shoreline are described in detail.