Subtended by a spathe-like sheath. Fruit an achene or loculicidal capsule. Seeds ribbed and with endosperm present. Placentation is axile or parietal. Habit is as annual or perennial, submerged, floating or emergent, semi-aquatic or aquatic herbs.
Leaves are simple, entire and alternate, opposite basal or whorled.
Sheathing at petiole is open, with the petiole often enlarged by air cells and with a stipule-like ligule.