Swimming through fresh waters in parts of South America and Asia is what one might consider an unexpected figure: the dolphin. It joins the ranks of the shark and the sea turtle as some of the oldest creatures on Earth. And while they're most commonly associated with oceans, dolphins—and porpoises—can actually be found in several major rivers on two continents.
When we think of dolphins and porpoises, we often don’t think of fresh water. But in parts of South America and Asia, several rivers are home to these charismatic species. Dolphins are among the world’s oldest creatures, along with some species of turtles, crocodiles and sharks. They provide important indicators of the health of rivers.