This research is carried out to study the bacteriological biodiversity and quality of water during premonsoon, monsoon and post-monsoon in Panvel lakes, Maharashtra, India. Most Probable Number (MPN) count was carried out by using Mac Conkey’s broth in order to classify the lakes into different categories. Pathogenic bacteria colonies were isolated from water samples collected from different lakes, by spread plate method. After incubation, different colonies from incubated plates were picked; purified by repeated sub-culturing before being examined for gram reaction, microscopically bacteria were identified into positive or negative, cocci or bacilli, rod or spiral. Biochemical analysis was carried out using different tests. The results were analyzed using Bergey’s manual of systematic bacteriology. Many different types of bacteria were isolated from water samples that helped in classifying the lakes and knowing the bacterial loads of each lake.