Prostrate often villous herb, rooting at the nodes or floating, with pneumatophores restricted to submerged parts; flowering stems ascending.
Leaves alternate, usually oblanceolate to obovate, usually 1–10 cm long, 4–30 mm wide, base tapering; petiole 2–30 mm long.
Flowers solitary in upper leaf axils; bracteoles triangular, near middle of ovary. Sepals 5, triangular. Petals 10–20 mm long, yellow, darker at base. Stamens 10.
Fruit terete, 10–30 mm long, 2–4 mm diam., 10-ribbed, thick-walled and tardily dehiscent; seeds in each loculus in 1 row, embedded in endocarp.