The narrator tells readers in a simple, expository present-tense what a riffle and a pool are and why the presence of “aquatic macroinvertebrates” shows that water is healthy. They find a dragonfly nymph, a water penny, a mayfly nymph, and a caddisfly larva as they pick up rocks and sift through leaf packs. Their process of careful inquiry is as informative as their findings in this instructive exploration of a natural habitat. The text is rendered in a large font, good for precocious readers, and the pictures combine painted line drawings of the children and the environment with clear, enlarged images of the invertebrates in question. The backmatter includes drawings of additional macroinvertebrates, a field-notebook page, a life cycle matching activity, and a link to online quizzes and games...A handy companion for outdoor exploration.