Ruppia, also known as the widgeonweeds,[4] ditch grasses or widgeon grass, is the only extant genus in the family Ruppiaceae, with eight known species.[5] These are aquatic plants widespread over much of the world.[3] The genus name honours Heinrich Bernhard Rupp, a German botanist (1688-1719).[6] They are widespread outside of frigid zones and the tropics.