The stems and leaves are a source of nesting material and food for aquatic birds and mammals. Fossils in the Paleocene with some more questionable fossils in the Upper Cretaceous. Inflorescence a dense head of sessile flowers attached to the main axis with male flowers above female flowers. Fruit an achene with persistent style and tepals. Seeds with mealy endosperm present.
Placentation is apical or basal.
Habit is as aquatic or semi-aquatic perennial herbs. Leaves are simple, linear and entire, two-ranked and alternate. Often thick and spongy with sheathing at the base.