A flexible water gate is described that is suitable for retaining water in a port, canal or river estuary. The gate is both economical to build and maintain and comprises a gate control means that allows a flexible membrane to be controllably moved between a closed and open position as required. A flexible flood control barrier that comprises one or more of the aforementioned flexible water gates. These gates are deployed side to side and provide an economical way of providing flood protection to an area susceptible to flood tides. When not in use the flexible membranes of the flexible water gates can be stored on the riverbed so permitting unrestricted access for marine vessels.