La Plata DolphinThey have the largest beak of any cetacean. The blowhole is crescent shaped and the dorsal fin has a long base and a rounded tip. They have large flippers. They move very smoothly and slowly. Coastal Atlantic waters of South America and the tropical waters of Capricorn to Argentina. Frequent sightings indicate that they do not migrate. Social system/Group sizeUsually seen in groups of 2 - 15. Pollution and habitat degradation. They belong to the group of the river dolphins that live in oceans and saltwater estuaries.