When four friends are horrified to find their swimming hole filled with green slime, a mysterious naturalist named Riparia helps the children understand why the water became polluted―and together they figure out how they can bring clean water back to the river they all love. At the back of the book is a list of the animals that appear in the story and an invitation to find them all. This lively story about non-point source pollution is filled with both information and action. Realistic, lush illustrations by Olga Pastuchiv illuminate the children's passion for their river and the ecosystem it supports. Grade Level: 2nd - 5th