Rhizomes creeping, 3-4 mm in diam. Stems abbreviated, internodes 3-5 mm; persistent fibrous leaf bases blackish brown. Leaves alternate, linear, 25-100 cm × 1-2.5 mm, 3-veined, margin entire or irregularly denticulate toward apex, apex obtuse and retuse; sheaths 4-20 cm, amplexicaul. Spathe 1, with flattened stalk 1-3(-7.5) cm and shrimplike sheath; projections ovate-lanceolate, alternate with flowers. Anthers with 2 filiform thecae. Carpels sagittate to cordate at base. Fruit semilunate, 2-2.5 × 4-5 mm; beak apical. Fl. and fr. Mar-Aug. 2n = 16, 20.
Fine gravel or sand near low tide mark; sea level to ca. 8 m. Coasts of Hebei, Liaoning, Shandong [coasts of Japan, Korea, and Russia (Far East)].