Witness King Tides (WKT) is a citizen-science project collecting photos of the shoreline at the time of highest predicted tide each year, with the aim of indicating the flooding that may occur routinely with sea-level rise. However, effects such as storm surges may affect the results, leading to significantly lower tides than expected. Tidal observations from the GESLA-2 global database are analysed to indicate regions of the world where WKT should perform well and others where it would not.