River swimmers are aquatic animals that spend most of their time in the water. Two examples of river swimmers are otters and shads. Otters are semi-aquatic mammals that inhabit rivers, lakes, and coasts. They have webbed feet and a streamlined body that helps them swim quickly. Shads are a type of fish that live in freshwater and saltwater rivers. They have a slender body and a forked tail that helps them move through the water with ease.