This book presents information on common-to-rare organisms from around the world that inhabit freshwater habitats. The first six chapters focus on organisms from the very small (e.g., protozoa, zooplankton, and fairy shrimp) to the huge (e.g., hippos, freshwater sharks, and giant turtles), while the last four chapters provide information on aquatic ecosystems (lakes, streams, caves, and wetlands). Included in this last section are the physical nature of the system and how that influences the kinds of animals living there. This unique "nature" book, incorporating information from around the world on both aquatic systems and organisms, is written to attract the interest of a wide group of non-academic readers.