the la plata dolphin is found in the coastal atlantic waters of southeastern south america, including the río de la plata estuary. its distribution ranges from the tropic of capricorn near ubatuba, brazil, south to península valdés, argentina. it is the only member of the river dolphin group that lives in the ocean and saltwater estuaries, rather than freshwater. although some members of the species do spend portions of their lives outside of river systems, many individuals live their entire lives within rivers, never venturing into the ocean proper.