Data provided are monthly surface water layers extracted from Sentinel1A SAR data for 3 districts in India (Shivamogga, Sindhudurg, Wayanad) for the year 2017 and 2018. Surface water body layers were mapped using an average monthly threshold value extracted from the image backscatter histogram. The average threshold value excluded the monsoon months due to the difference in water and not water area. The threshold value was slightly lesser than the mean threshold value. The end product was validated using field data which resulted in user and producer accuracies. Monthly surface water body layers were not produced for a few months due to the non-availability of Sentinel 1 data. The work was supported by MRC, AHRC, BBSRC, ESRC and NERC [grant number MR/P024335/1] and NERC - SUNRISE project [grant number NE/R000131/1] Full details about this dataset can be found at https://doi.org/10.5285/3c23fea1-5b27-4b01-b9ef-fc13346cfedc