A freshwater marsh is a marsh that contains fresh water. They are usually found near the mouths of rivers and are present in areas with low drainage. It is the counterpart to the salt marsh, an upper coastal intertidal zone of bio-habitat which is regularly flushed with sea water.
The Florida Everglades represent the largest contiguous freshwater marsh in the entire world. This immense marsh covers 4,200 square miles (11,000 km2) and is located in the southern tip of Florida. Continued human development, including drainage for development and polluted agriculture runoff, as well as alterations in the water cycle threaten the existence of the Everglades. The remaining parts of the Everglades are grasses, sedges and other emergent hydrophytes.