Situational sea awareness (SSA) is a field of applied oceanography that relies on operational oceanographic products (analyses, re-analyses and forecasts) to inform users about environmental conditions at sea, including early warning for marine extremes and hazards. The key is to develop information technologies capable of disseminating user-oriented information that is based upon rapidly changing data from wind, waves and current forecasts. Situational sea awareness is useful for all maritime operations, from ship routing to search and rescue, offshore hydrocarbon exploration and fisheries, where the knowledge of the environmental conditions is required to carry out operations at sea safely and efficiently. The environmental data of interest are the meteo-oceanographic analyses and forecasts as well as the related positions of objects and substances in the whole water column.