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C-band observations of the SAR backscatter from the Envisat ASAR (2005-2012) and Sentinel-1 (2014-ongoing) instruments are reviewed to understand their suitability to detect of open water bodies. The temporal variability (TV) and the minimum backscatter (MB) of ASAR backscatter were fed to a simple algorithm based on thresholds to obtain an indicator of water bodies globally with a spatial resolution of 150 m. Confusion occurred either in the case of irregular acquisitions of ASAR images or in cold and arid regions where the multi temporal metrics based on the multi-year ASAR dataset were often similar to values obtained over open water bodies. With Sentinel-1, there are clear chances to improve the mapping of water bodies considering the dual-polarization capability, the higher spatial resolution and the more consistent observation strategy. First examples from a test site in Sweden show that average and minimum cross-polarized backscatter are suited for water body mapping.