Lakes are a crucial source for total potable water worldwide and a particular one, like Ashtamudi Lake, was chosen as the study area for this research. The physicochemical and biological cycles of lakes in connection with the Indian southwest coast were also studied. Eighteen surface water samples were collected from different locations from Kanjirakkottu Kayal, situated at the southeastern edge of Ashtamudi Lake, and were analysed for various physicochemical and biological parameters using the procedures outlined in standard authorities like APHA and IS 10500. The major findings of this study are majority of the locations are under threat by some increased values in parameters like Electrical conductivity, Total dissolved solids, salinity and total hardness, etc. While checking the BOD of samples, it is obtained that eleven out of the total locations are out of the limit of 2 mg/L. In the case of parameters like nitrate, nitrite, phosphates and silicates, the majority of locations are within the permissible limit by standard authorities. But, while considering sulphate except locations 9 and 11, all are under increased sulphate concentration. For assessing the overall quality of water samples, the water quality index (WQI) was calculated by taking Ca2+, Mg2+, Cl−, NO3−, SO42−, alkalinity, total hardness, DO and BOD into consideration. From the calculated WQI, it can be concluded that a large fraction of the chosen locations is under threat by having values greater than 300. The principal component analysis (PCA) suggests that the quality of water varies significantly across all sites and gives rise to mainly two kinds of clusters. While interpreting the Pearson correlation analysis, there is high multicollinearity among EC, TDS, Cl and sulphate. The salinity of surface water ranges from 196.6 mg/l to 79,740 mg/l. So, it clearly indicates some effect of the southwest coast on the lake system. Finally, in the Kanjirakkottu Kayal region, only the ninth and 11th locations have water which is consumable. In conclusion, the water quality of Kanjirakkottu Kayal in Ashtamudi Lake is poor at the majority of locations, with elevated levels of contaminants and poor WQI scores, highlighting the need for immediate attention to address this pollution and mitigate it.