Herbs, perennial, not cespitose, stoloniferous, aquatic. Culms solitary, trigonous. Leaves basal; ligules present, ciliate; blades flat to V-shaped in cross section, prominently keeled on abaxial surface. Inflorescences terminal, umbellate heads or capitate; involucral bracts 1-6+, spreading, leaflike. Spikelets: scales 5-10+, 3-ranked, spirally arranged, each subtending flower. Flowers bisexual; perianth absent; stamens 3; styles 2-fid, linear, base persistent. Achenes plano-convex, margins and apex corky.