[1][2] Marshes in general are humid areas, low-lying, swampy terrains that are flooded by sea water during high tide.

Where the marshes have been transformed, among others for the development of marine aquaculture, bodies of water distributed as ponds and pools are the main elements of the landscape.

The vegetation consists of communities of halophytes, typical of these types of habitats and adapted to the daily tidal flooding.

The homogeneity of the color of the scrub is contrasted with the presence of water, an element which carries great attraction.

The geomorphology shows a large flat coastal fringe, a transition from land to sea with seasonal fluctuations.

The bird life (see Fauna for more details) of the marsh includes many species of water fowl which bring great value to the unit.

In the southern part it is closely bound to the city of Isla Cristina, in the north the marsh is bordered by the Verde Litoral road.

It is a degraded marsh, transformed long ago for the exploitation of table salt and currently developing aquaculture.

The 311 hectares hydrophilic, halophytic grasslands with tidal influence have been transformed with the repopulation of tamarisks (Tamarix canariensis, Tamarix africana) and the formation of well-preserved salt marshes of salicornia (Arthrocnemetea), and grasslands of eel grass (Spartina densiflora).

An important formation of halophytes (sarcocornia), its characteristics are similar to that of the caño del puntal (see flora for more details).

To the west they are limited by the town of Ayamonte and by the Sapal Nature Reserve of Castro Marim and Vila Real de Santo António (belonging to the Guadiana river).

To the north the Vía Verde Litoral road, to the south Isla Cristina city and the Atlantic Ocean and an area of Mediterranean pine forest and dunes of ICONA (Instituto para la Conservación de la Naturaleza) and finally to the east an area close to the heart of the Redondela.

The Guadiana river brings sediments and maintains the integrity of the canals in the Isla Cristina marshes.

It is a place where the littoral and sediments dynamics have triggered a whole complex of coastal formations in the mouth of the Guadiana river estuary, resulting from the interaction of wind, waves, tides, the river, and human impact through tidal engineering works as seen.

[4] There are bird-watching points in several places by the marshes and Via Verde, from the discontinued Huelva-Ayamonte railway, crosses it lengthwise.

Other hiking routes with interpretation points are located at Prado Pond, Molino tidal marsh of Pozo del Camino and the Duque saltworks.

The most relevant animal species among the mammals is the otter (Lutra lutra) which is listed in Annex II of the Community Directive of Habitats (D. 92/43 CEE) as a Species of Community Interest for whose conservation are imposed the creation of Special Zones of Conservation.

[3] The flora most represented is mainly composed of: In this area there is also the maritime juniper, Juniperus oxycedrus subsp.

Although other rat species (Ondatra zibethicus or muskrat) and mice can be present, they don't exactly belong to this ecosystem.