Most of the changes scientists see on our planet are either visible to the naked eye or directly measurable. But changes to our water systems are among the most difficult to see. In this episode, we travel from the Antarctic ice sheet capturing over 60 percent of all freshwater on Earth, to massive groundwater aquifers that remain particularly elusive, to a freshwater system that acts as the primary economic, cultural, and environmental driver of southern Asia. In short, we go in search of hidden water.