Herbs, perennial, emergent, rhizomatous (forming mats to 5 dm), 0.5--1 dm. Rhizomes 1 mm diam., nodes not swollen. Culms repent, floating or submersed, usually profusely branched, terete, 0.5--1 mm diam. Cataphylls absent. Leaves: basal 1--5, cauline 1--4, small fascicles of short capillary leaves often on rhizomes and stems; auricles 0.1--0.8 mm, apex acute, membranaceous; blade terete, 1.6--3 cm x 0.1--0.3 mm. Inflorescences cymes, flowers 1--3 at 1--2 nodes, 1--4 cm, branches spreading to erect. Flowers: tepals reddish, oblong; outer tepals 1.8--2.8 mm, obtuse; inner tepals 2.2--4.4 mm, obtuse; stamens 6, anthers 3/4 to equal filament length. Capsules exserted, chestnut brown, 1-locular, ovoid to narrowly ovoid, 2.4--5 mm, apex acute proximal to beak, valves separating at dehiscence. Seeds ovoid, 0.3--0.5 mm, not tailed; body clear yellow-brown. 2n = 40. Fruiting late summer--early fall. Muddy, sandy or gravelly shores, fens in decomposed peat, fine muds rich in humus, and submersed in brackish pools; 0--200 m; Greenland; N.B., Nfld. and Labr., Ont., Que.; Maine. Flowers are rarely replaced by bulbils. Most Greenland collections are sterile.