'Formations of water bodies constituted by submerged, rooted, perennial phanerogams with often emerging flower spikes, in particular entirely immersed pondweeds of genus Potamogeton. Some habitats of this unit can be dominated by other species, such as Zannichellia palustris, Elodea canadensis, Elodea nuttallii, Ceratophyllum submersum, Myriophyllum spicatum and Najas marina.