Spain has designated Marjal de Almenara as its 75th Wetland of International Importance. The Site (Ramsar Site no. 2338) is a typical example of the marshes along the coast of the Gulf of Valencia, which formed as old lagoons gradually filled with sediments due to longshore drift; it is fed by fresh water from the nearby mountains.
The Site is made up of three small estanys (lagoons) ranging from 0.6 hectares to 6.2 ha and up to ten metres deep, which collect fresh water upwelling from nearby springs. It also includes freshwater marsh areas (some of which are almost permanently flooded), dunes, reed beds and salt marshes, as well as multiple canals and ditches. Some horticultural and citrus cultivation areas are included within the Site.
At least 40 taxa which are threatened or of special interest are present, including 26 bird species such as the globally threatened marbled duck Marmaronetta angustirostris. Six endangered and four endemic species of fish are recorded, including the critically endangered Valencia toothcarp Valencia hispanica. Three priority habitats of European importance are also present.
Despite being affected by human settlements, the Site has been little transformed and near-permanent flooding continues, while the coastal strip of the marsh is in a remarkably good state of conservation. The information centre La Casa Penya conducts educational activities.