This document discusses microorganisms found in water bodies. It describes that water habitats macroorganisms like fish and microorganisms like bacteria, viruses, and protozoa. Several pathogens that can be transported through water and cause illness are discussed, including bacteria like E. coli, parasites like Giardia lamblia and Cryptosporidium parvum, and the bacterium Legionella pneumophila. The document also covers viruses, fungi, algae and provides diagrams of microbial growth cycles and structures.