Banc d'Arguin is located on the Atlantic desert-coast of Mauritania, midway between Nouakchott in the south and Nouadhibou in the north. The park extends from Cap Timiris in the south, includes the Ile de Tidra, Ile d'Arguin and Cap d'Arguin to Pointe Minou in the north. The boundary extends a maximum of 60 km into the shallow sea and 35 km inland into the Sahara.
The park provides a unique example of a transition zone between the Sahara and the Atlantic. It is a vast area of islands and coastline, largely composed of windblown sand of Saharan origin, together with a large expanse of mudflats, with particularly well developed tidal flats in the vicinity of Tidra Island. Of the 15 named islands there are several up to 1 km wide and 5 km long, the largest; Isle of Tidra is 8 km by 35 km. The coastal waters between Cap Blanc and Cap Timiris are very shallow, and only reach a depth of 5 m at low tide even up to 60 km offshore. The arid inland component mainly comprises areas of sand hills and cliffs rising to 15 m. The mangrove swamp in the park is a relict of a previous humid geological period when Banc d'Arguin was a vast estuary mouth for rivers flowing from the Sahara.
The park lies at the junction between the Afrotropical and Palaearctic biogeographic realms. The vegetation of the sandy coastline, mudflats and islands is represented by halophytic species. The terrestrial component of the park is represented by Saharan vegetation with a limited Mediterranean influence. Shallow water vegetation comprises extensive seagrass beds and various seaweeds, and favourable habitat for the reproduction and development of fish.
Of the estimated 7 million wading birds that use the Atlantic flyway, approximately 30% spends the winter at Banc d'Arguin, which hosts the largest concentration of wintering waders in the world and one of the most diversified communities of nesting piscivorous birds in the world. At least 108 bird species have been recorded, representing both Palaearctic and Afrotropical realms. Wintering shorebirds number over 3 million and include hundreds of thousands of black tern and flamingo, ringed plover, grey plover, knot, redshank and bar-tailed godwit. The area is one of the most important wintering grounds for European spoonbill. Breeding birds include white pelican, reed cormorant, gull-billed tern, Caspian tern, royal tern and common tern, together with several species or subspecies with an African distribution, such as endemic heron and spoonbill and western reef heron.
Mammals include Dorcas gazelle, jackal, fennec fox, sand fox, sand cat, ratel and striped hyena. Marine mammals regularly recorded include killer whale, Atlantic humpbacked dolphin, common dolphin, rough-toothed dolphin, bottlenose dolphin and Risso's dolphin. Fin whale or common rorqual and common porpoise have also been sighted. A small population of about 150 monk seal is found at Cap Blanc, near Nouadhibou. Four species of turtle frequent the area: green, loggerhead, hawksbill and leatherback. Fish are one of the most important components of the fauna. The shallow tidal flats act as important breeding and nursery areas.
Neolithic archaeological sites and vestiges of the Almoravide civilization are found on a number of the islands. The local people, the Imraguen or Amrig, relate many of their customs to the natural environment. Even their name literally means 'the ones who gather life'. Imraguen tribesmen still maintain their age-old lifestyles, based almost exclusively on harvesting the migratory fish populations using traditional sailing boats. Fishing techniques, unchanged since first recorded by 15th-century Portuguese explorers; include the unique symbiotic collaboration with wild dolphins to catch schools of grey mullet.
The 500 or so Imraguen people live in seven villages within the park, but are dependent on water supplies collected outside the boundary. They base their economy on subsistence fishing using traditional methods. Use of the area by nomads is decreasing due to the area becoming more desertified. The Baie du Levrier and the harbour of Nouadhibou have become important bases for international fishing fleets.