The purpose of this assessment probe is to elicit students’ ideas about a major freshwater resource, groundwater. The probe is designed to find out how students visualize groundwater, which can be challenging as it is very different from water resources they see on the surface of Earth. It is best used with upper elementary, middle, and high school students, and can be extended by asking students to draw a conceptual model showing what they think groundwater looks like from a cross-sectional view below Earth’s surface. A materials list, teacher background information, references, assessment, and outcomes are provided. This book selection includes the Table of Contents, Foreword, Preface, Acknowledgments, About the Authors, Introduction, and Index.