During the studies on fouling diatoms in Zuary estuary the overlying surface diatoms were also studied for comparison. In all 66 spp. of planktonic diatoms has been recorded, belonging to 29 genera. Out of these, 36 species (16 genera) were Pennales and 30 (13 genera) Centrales. The common diatoms observed were Chaetoceros borealis, C. decipiens, Biddulphia regia, B. sinensis, Coscinodiscus conscinnus, C. subtilis, C. grani, Navicula inflexa, N. oblonga, Amphora turgida, A. ovalis, Nitzschia sigma var. regidula, N. longissima var. closterium, Thalassiothrix nitzscheoides, Rhizosolenia stolterfothii and R. shrubsolei. Pennales were dominant over Centrales both in diversity of genera and species. Minimum number of diatoms were recorded during monsoon and maximum during postmonsoon and premonsoon months. Solitary forms were found in abundant quantity, while colonial forms were few. Occassional blooms of Chaetoceros sp. were only observed. Interestingly most of the fouling diatoms were represented in plankton also.