Potamogeton gramineus; the Various-leaved Pondweed is a common pondweed on Iceland. This plant grows both with submerged leaves and floating leaves in ponds and lakes. On Iceland there are a few more Potageton species growing in ponds, lakes, waterways. They can be differentiated by their leaf-shapes. One has to take into account that submerged leaves and surface leaves can differ. On the page of the Red Pondweed a table is presented how to differentiate these species. You can open this table here
Alas I do not have pictures of other Potamogetonaceae (pondweed family) members yet.
Potamogeton_gramineus / Various-leaved pondweed is a member of the pondweed family (Potamogetonaceae).