The consumption of bivalve mollusks can represent serious risks to the public health, because they reflect the conditions of the environment directly. This way it is considered of extreme importance the consumption of oyster without contamination. This paper aims of studying the water microbiology quality from the Cooperostra (cooperative of producer) in Cananéia, SP. It was analyzed in the water: total and fecal coliforms. The results found in the water were not satisfactory, suitable with the Brazilian legislation, except for the same month. The intensity of seasonal interferencewas discovered in the microbiological count in the water was verified high positive correlation.