Distribution: Occurring along the coast of Washington where rocky; Alaska to California.
Habitat: Rocky intertidal and sub-tidal zones.
Conservation Status: Not of concern
Dioecious, submersed, aquatic perennials from extensive rhizomes, the stems mostly unbranched, flat, 0.5-4 dm. long.
Leaves alternate, linear, 5-15 dm. long and 2-4 mm. broad, sheathing at the base.
Both staminate and pistillate flowers in two rows on fleshy, one-sided spikes, the pistillate surrounded by a sheath; each staminate flower consists of a single, sessile anther, the inflorescence about 5-6 cm. long; each pistillate flower consists of a single, 2-carpellary pistil with 1 style and 2 stigmas, the inflorescence 2-4 cm. long.
Utricle 3-4 mm. long, sagittate at the base.