The Diep/Rietvlei Estuary is a low-inflow, choked coastal lagoon system located within the City of Cape Town, South Africa. It is a cool temperate estuary that is susceptible to becoming hydrologically disconnected from the ocean by a sand barrier, which can lead to long water residence times and the development of hypersaline conditions. This dynamic creates a unique and variable estuarine environment that supports specific vegetation and aquatic life. The system is recognized for its ecological value but also faces threats from infrastructure damage during significant wave and river discharge interactions.