Description from Flora of China
Herbs, aquatic, perennial, rhizomatous. Leaves all basal, aerial, floating, or submerged, ovate to elliptic; floating leaves deep green, large; aerial leaves subleathery, with erect petiole; submerged leaves usually smaller. Inflorescences paniculate or racemose, much branched; branches whorled, each whorl with 3-6 branches; bracts lanceolate. Flowers pedicellate, verticillate, bisexual. Petals usually larger than sepals. Stamens 6-12. Carpels few to numerous in a single whorl, free, each with 1 ovule. Fruitlets drupaceous, with woody endocarp and spongy exocarp, swollen or slightly compressed, with a short beak.
About three species: Africa, Asia, Australia, Europe; two species in China.