Widgeon grass grows in a tremendous range of salinities, including fresh, brackish and saline waters. It has been observed in Baffin Bay, Texas at salinities exceeding 100. Ruppia is generally found in the soft sediments of wind-protected lagoons and bays. This species closely resembles shoal grass but can be distinguished at maturity by its morphology. Widgeon grass has multiple slender, threadlike blades that protrude in an alternating fashion along the stem. These blades appear bushy and fan-like. Root and rhizome structures do not form thick, extensive mats making them easy to uproot.