[3][4][5][6][7] Roughly 80% of the Pantanal floodplains are submerged during the rainy seasons, nurturing a biologically diverse collection of aquatic plants and helping to support a dense array of animal species.

[citation needed] The Pantanal covers about 140,000–160,000 km2 (54,000–62,000 sq mi)[8][9] of gently-sloped basin that receives runoff from the upland areas (the Planalto highlands) and slowly releases the water through the Paraguay River and tributaries.

The formation is a result of the large, concave, pre-Andean depression of the Earth's crust, related to the Andean orogeny of the Tertiary.

The Pantanal is a tropical wet and dry region with an average annual temperature of 24 °C (75 °F) and rainfall between 1,000 and 1,250 millimetres (39 and 49 in) per year.

[3] Flood waters tend to flow slowly (2 to 10 cm (0.79 to 3.94 in) per second[3]) due to the low gradients and high resistance offered by the dense vegetation.

The reason for this remains speculative: it may be due to the growth of toxin-producing bacteria in the deoxygenated water rather than as a direct result of lack of oxygen.

[3] Forests usually occur at higher altitudes of the region, while grasslands cover the seasonally inundated areas.

[3] According to Embrapa, approximately 2,000 different plants have been identified in the Pantanal biome and classified according to their potential, with some presenting significant medicinal promise.

Unlike other decomposing animals, the apple snails have both gills and lungs, making it possible for them to thrive in anoxic waters where they recycle the nutrients.

[13][14][15] Among the rarest animals to inhabit the wetland of the Pantanal are the marsh deer (Blastocerus dichotomus) and the giant river otter (Pteronura brasiliensis).

Parts of the Pantanal are also home to the following endangered or threatened species: the hyacinth macaw (Anodorhyncus hyacinthinus) (a bird endangered due to smuggling), the crowned solitary eagle (Buteogallus coronatus), the maned wolf (Chrysocyon brachyurus), the bush dog (Speothos venaticus), the South American tapir (Tapirus terrestris), and the giant anteater (Myrmecophaga tridactyla).

This 1,350 km2 (520 sq mi) park, established in September 1981, is located in the municipality of Poconé in the State of Mato Grosso, between the mouths of the Baía de São Marcos and the Gurupi Rivers.