Indian Sundarban lies in the south-western part of the Ganges-Brahmaputra Delta and supports a 4.43 million strong population. The agrarian economy of Sundarban is dominated by rainfed subsistence rice farming. Unavailability of upstream fresh water, high salinity of river water of up to 32ppt, soil salinity ranging between 2dSm-1 to 19dSm-1, small land holdings of per capita 840 sq. metre and inadequate irrigation facilities are serious constraints for agricultural production in Sundarban. This paper assesses Cropping Intensity, Irrigation Intensity and Man-Cropland Ratio from Agriculture Census (2010-11) data and estimates the seasonal water demand for agriculture in different blocks of Sundarban. The research exposes the ever increasing population pressure on agriculture with an average Man Cropland Ratio of 1745 person/sq.km. In 2010-2011, the average cropping intensity was 129.97% and the irrigation intensity was 20.40%. The highest cropping and irrigation intensity have been observed in the inland blocks where shallow ground water is available for agriculture on the contrary, the lowest values have been observed in the southern blocks, due to existence of saline shallow ground water. The annual water demand for agriculture in Sundarban has been estimated as 2784 mcm. Available water from 70000 freshwater tanks and around 8000 numbers of shallow tube wells are not sufficient to meet the agricultural water demand. Existing irrigation sources and rainfall of 343 mcm fall far short of the water demand of 382 mcm during peak dry Season. Unavailability of fresh water restricts the food production, which endangers the food security of 87.5% of the people in Sundarban. To ensure the food security in changing climatic condition, expansion of irrigation network and harnessing of new water sources are essential. Large scale rainwater harvesting, rejuvenation and re-connection of disconnected river channels, artificial recharge within shallow aquifer to bring down its salinity can be some of the major policy options to meet the water demand for agriculture in Sundarban.