Annual or perennial, succulent hydrophytes. Leaves upright, sagittate or cuneate at the base, glabrous or pubescent. Inflorescence upright, scapigerous raceme of 4-7 whorls of 3-flowers each. Flowers bisexual and male (plants polygamous), white, bisexual flowers towards base of raceme, male ones towards apex; bracteate. Sepals patent, reflexed after anthesis, persistent. Petals white. Stamens 6, antisepalous, filaments dilated towards the base. Carpels 15-numerous, crowded on the thalamus; ovaries ovoid; style ventral; pistillode absent in male flowers. Achenes turgid with lateral air sacs between endocarp and ridged exocarp. Seed and embryo curved, testa membranous.