Perennial aquatic herbs, leaves petiolate, subopposite or alternate, lamina entire to somewhat wavy. Inflorescence an axillary in umbellate clusters. Calyx deeply 5-lobed. Corolla deeply 5 lobed, rotate lobes with fringed appendages, deciduous. Disc 5-lobed at the base of fleshy ovary, lobes alternating with the stamens. Ovary superior, unilocular with few to many ovules. Style simple, short, stigma 2-3 lobed. Capsule ellipsoid or ovoid, indehiscent. Seeds numerous, ovoid-orbicular with usually finely reticulate tests.