The swamps are generally set back a few kilometers or two from the sea by the saltwater-affected Sunda Shelf mangroves The relatively fertile, flat soil has led to much of this ecoregion being converted to agriculture.

[1][2][3][4] The freshwater swamp forests of the southwest coast of Borneo occur where rivers on flat alluvial plains meet the coastal mangroves.

The mature forest supports a wide variety of tree and shrub species, including the families and genera of Adina a shrub, Alstonia (some species of which are of commercial value for timber), Campnosperma, Coccoceras, Dillenia, Dyera, Erythrina, Eugenia, Ficus, Gluta, Lophopetalum, Memecylon, Pentaspadon, Shorea, and Vatica.

The most common primate in the freshwater swamp is the vulnerable Crab-eating macaque (Macaca fascicularis).

The freshwater swamp is also home to the critically endangered Bornean orangutan (Pongo pygmaeus).