Water Hyacinth is an aquatic macrophyte and highly invasive species, indigenous to Amazonia, Brazil and tropical South America. It was first introduced to India in 1896 and has now become and environmental and social nuisance throughout the country in community ponds, freshwater lakes, irrigation channels, rivers and most other surface waterbodies. Considering the adverse impact the infesting weed has, a constant monitoring is needed to aid policy makers involved in remedial measures. Due to the synoptic coverage provided by satellite imaging and other remote sensing practices, it is convenient to find a solution using this type of data. This paper looks at the use of Synthetic Aperture Radar (SAR) Sentinel-1 to detect water hyacinth at an early stage of its life-cycle. While SAR has been used prominently to monitor wetlands, the technique is yet to be fully exploited for monitoring water hyacinth and we seek to fill this knowledge gap. We compare different change detection methodologies based on dual polarimetric data. We also demonstrate how Sentinel-1 can be used to monitor this type of aquatic weeds in our study areas, which is Vembanad Lake in Kuttanad, Kerala.