“What is an estuary?” is a video project in the context of the OCEÁNTICA project for the dissemination of knowledge related to the sea. Considering the frame of Vigo and Galicia, “What is an estuary?” seeks to provide a definition of estuary from different points of view: geography, history, economy, etc., and give account of the influence of this geographical feature in society, in their way of life, in their traditions and even in the arts and literature.