This data was collected to investigate the relationship between human activities and size distribution of gastropods on rocky shores. It was predicted that there would be a negative correlation between the level of human activity and the average size of gastropod species such as Cellana tramoserica, Austrocochlea constricta, Turbo undulata, Thais orbita and Nerita atramentosa, which are collected by humans for bait and occasionally for food. Sampling was undertaken in May 1990 and February/March 1991 at 6 locations within the Bunurong Marine Park, Victoria. On each sampling occasion the size of 100 snails of each species was measured at each site.