Worldwide in aquatic environments. As aquatic ornamentals and important food source for aquatic animal species and birds.
Flower is large and showy.
Inflorescence a solitary flower borne on the surface of the water. Endosperm is present. Placentation is unique, the ovules being borne over the inner surface of the locule. Habit is as an aquatic, perennial herb. Leaves are simple and cordate or orbicular, alternate and either immersed or borne on the surface of the water.