Dolphins can at times be found in rivers as well. River dolphins are four living species of dolphin, which reside in freshwater rivers and estuaries. They are classed in the Platanistoidea super family of cetaceans. Three species live in fresh water rivers.The fourth species, the La Plata Dolphin, lives in salt-water estuaries and near-shore marine environments. However, it is scientifically classed in the river dolphin family rather than the oceanic dolphin family. These species may never venture towards the oceans.hree species live in fresh water rivers. The fourth species, the La Plata Dolphin, lives in salt-water estuaries and near-shore marine environments. However, it is scientifically classed in the river dolphin family rather than the oceanic dolphin family. These species may never venture towards the oceans.