Aquatic, perennial herbs with rhizomes, rooted in the ground. Stipules 0. Leaves alternate, floating and usually ± peltate. Flowers bisexual, actinomorphic, solitary, pedunculate, large and handsome, floating, emergent or, rarely, submerged. Sepals 4-6, green or coloured. Petals 5-numerous, some ± sepaloid. Stamens numerous, sometimes with petaloid filaments. Carpels 6-numerous, united. Ovary superior or inferior with 1 or numerous ovules. Fruit fleshy or spongy. Seeds with a fleshy aril.