Aquatic herbs. Leaves alternate, opposite or whorled, floating or submerged; submerged leaves, if present, opposite or whorled, dissected, with mostly dichotomous divisions; floating leaves alternate, circular, elliptic or rhombic, peltate. Flowers floating (in Australia), axillary, solitary, bisexual, actinomorphic; sepals 3 or 4, petals 3 or 4, similar, petaloid; stamens 3–c. 40, anthers extrorse; carpels superior, 1–18, free, 1-locular, ovules 2–3, placentation parietal, stigma subsessile, entire. Fruits indehiscent; seeds 1–3.
2 genera with c. 8 species in tropical to warm-temperate regions; 1 native and 1 naturalised species in Australia.