Plants perennial herbs of fresh or alkaline brackish waters, glabrous, rooted in the substrated with creeping sympodial rhizomes; stems elongated, submerged or floating, rarely prostrate on wet mud. Leaves alternate, sometimes opposite or in whorls of three, with sheathing bases, often with stipules; ligules often present, long, sometimes bifid; blades linear, sometimes with an apical pore. Inflorescences in axillary or terminal bracteate spikes and more or less clustered, with 2 or more flowers. Flowers inconspicuous, radially symmetric, bi- or unisexual, if bisexual the plants unisexual or bisexual; tepals 3-4, separate, forming a tube, or absent; anthers 4 in bisexual flowers, 1 in male flowers; ovaries 1-8, free, sessile or stipitate, each with 1 ovule; styles simple, often short; stigmas sometimes enlarged. Fruits nutlets or drupes; seeds without endsperm.
As described above, Potamogetonaceae includes 4-7 genera and about 115 species because the Angiosperm Phylogeny Group endorses expanding it to include what used to be known as Zannichelliaceae. Only one genus, Potamogeton, is known from Somaliland and Somalia.
The above treatment is based on the treatment in the Flora of Somalia and information on the Angiosperm Phylogeny Website
References
Lye, K.A. (1995). Potamogetonaceae in M. Thulin (ed.) Flora of Somalia 4: 14-15.