Myriophyllum alternifolium; the Alternate Water-milfoil is a rather common water-plant on Iceland. Basically one can find it anywhere in ponds and lake-sides except for the interior highlands. The foliage grows under water but the inflorescence stalks rise above the water level. A similar species with coarser leaves is Myriophyllum sibiricum (Common Water-milfoil). This species grows mainly in the (central) northern regions of Iceland
It is a member of the Water-milfoil family (Haloragaceae).