Perennials; stem a rhizome, corm or tuber. Leaves ovate to orbicular with a deep sinus, cordate or subpeltate, mostly floating, if submerged then usually sagittate and delicate. Flowers floating with flexuose pedicels or borne above the water on rigid pedicels; sepals usually 4; petals numerous, showy, in many series, often passing into stamens or staminodes; stamens with or without appendaged connectives; ovary globose; carpels 3–35; stigmatic disc concave, obconical or almost flat. Fruit a berry enclosed by the perianth, drawn under water by spiralling pedicel before ripening; seeds numerous; aril bell-shaped.
About 60 species, cosmopolitan; c. 18 species in Australia, 5 introduced.