Ruppia megacarpa R.Mason

Submerged, rhizomatous perennial; turions absent; stems erect, to 2.5 m long (usually 20–30 cm), usually zig-zag. Leaves 5–25 cm long, (0.4–) 0.5–1 mm wide, bidentate or truncate. Inflorescence presented at water surface for pollination on peduncle to 1 m or more long; peduncle coiling after pollination and pulling developing fruit below surface. Flowers 2 with (2–) 4 (–6) carpels. Carpels initially subsessile; stipe lengthening as carpel matures until much longer than carpel. Fruiting carpels asymmetric, 3–4 mm long, 2–3 mm wide; endocarp with stylar beak (0.5–) 1–2 mm long and rounded triangular perforation on each side.

Grows in brackish to hypersaline coastal lagoons, estuaries and inlandlakes.