Water horsetail, also known as Equisetum fluviatile, is a type of plant that grows in damp areas, such as marshes, swamps, and riverbanks. It is a member of the Equisetaceae family, which includes other species of horsetail. There are several synonyms for water horsetail, including Marsh Horsetail, Swamp Horsetail, Water Scouring Rush, and Watergrass. These names describe the plant's habitat, appearance, and use. Water horsetail has been used for medicinal purposes, such as treating urinary tract infections, and as a source of silica for polishing metal. Its long, green stems can also be used in floral arrangements or as a decorative element in landscaping.