Monoecious, emergent. Stems short, rhizomatous. Leaves basal, submerged or floating; petiole terete; blade linear-lanceolate or not expanded, apex acute, base attenuate. Inflorescence scapose, emergent, racemose, the lower whorls of carpellate flowers, the upper whorls of staminate flowers. Flowers short-pedicellate or sessile; sepals ovate, persistent; petals white to pinkish, reduced or smaller than sepals; staminate flowers with 3 stamens, carpels reduced to nectaries; carpellate flowers with receptacle slightly curved, with 3 staminodes and 3-6 free carpels. Achenes obovoid, rounded, weakly sculptured, with 3 dorsal keels.