People are increasingly aware of the role that water has in shaping society and how it impacts quality of life. This is the first book to provide a holistic perspective on water, capturing the full breadth of the science, technology, policy, history, and future outlook for the most important substance on earth - written at a level accessible to non-experts in each of these areas. Water is shockingly bizarre in its properties and of unsurpassed importance throughout human history, yet so mundane as to often be invisible in our daily lives. In Water Is ..., the two Seths (Darling and Snyder) walk the reader through all of the diverse perspectives on water. The journey begins with an exploration of the mysteries of water's properties on the molecular level, zooming out through its central role at biological and geological scales. Next, the Seths travel through the history of human civilization, highlighting the fundamental part water has played throughout, including the complexities of water policy, privatization, and pricing in today's world. Attention then turns to technology and innovation, emphasizing the daunting challenges dictated by increasing water stress and a changing climate as well as the enticing opportunities to achieve a secure global water future. Water is arguably the single most interdisciplinary topic. Students in business, policy, history, science, and engineering can best position themselves to make an impact by learning about the entire range of diverse, unexpected, and fascinating angles on water.