Geoenvironmental dynamics of habitats for a number of species and their linkage with biological activity and species diversity remain poorly understood. This study presents an ecohabitat chart showing the relationships between the habitat geophysical environmental conditions and diverse biological activities of species that belong to Arthropoda, Mollusca, and Annelida, from juvenile to adults, on sandy beaches and sandflats. The in situ sediment hardnesses of fifteen sandy beaches and sandflats varied considerably due to suction development and suction-dynamics-induced sediment compaction. The diversity of macroinfauna exhibited distinct changes in their responses to variations of such geophysical environments. Under critical conditions, biological activities, including burrowing, burrow development, and physiological activity, were hindered or prevented from taking place. The developed ecohabitat chart represents a complex interrelationship of the critical geophysical environment among species and revealed a species diversity–geoenvironmental dynamics relationship that was found to be consistent with field evidence. These results demonstrated the important role of the geoenvironmental dynamics in the distributions of species, accounting for the cause and effects involved. The present study may effectively contribute to novel habitat design, assessment and management for the conservation and restoration of sandy beaches and sandflats.