Observations were made on a sandy beach at Calangute Goa, during the monsoon months of 1971. Prevailing unstable conditions caused dynamic changes in the beach ecology. The average spread of the intertidal region was 19 m with a gradient of 1 in 10. The sand was predominantly coarse and the diameter of particle size varied between 450 and 900 µ, Organic carbon in the sand ranged from 38 to 732 /tµ/gm. The temperature regime of the sea water and interstitial water was 23.9 to 25.9° C, whereas on the sand surface, values upto 32.5°C were observed. , Salinity of the surface sea water varied from 22.05 to 34.56 % (:. The average biomass during the period was 11.86 g/m'. Polychaetes, mainly, Pisionidens indica occurred at mid and low tide levels. Pelycypods Donax incarnatus, Domx apperitus, and mole crab Emerita holthuisi accompanied by ampbipods and isopods were abundant in the wash zone.