Rigid hornwort (Ceratophyllum demersum), lake Jezioro Czarnoglowy, Oder Delta water catchment, Poland.

Commonly known as hornwort, rigid hornwort, coontail, or coon's tail,is a species of Ceratophyllum. It is a submerged, free-floating aquatic plant, with a cosmopolitan distribution.

The Oder Delta is located in the Baltic coast in Germany and Poland. Oder Delta is a European Rewilding area since June 2015, and the region is unique with a rich mosaic of large wild freshwater and marine ecosystems. It is strategically located on one of the ecological crossroads in Europe.The wild jigsaw of habitats includes rivers, heathlands, deltas, marshes, vast reed beds, forests, wild grasslands and bogs. IThe Oder Delta is rich in biodiversity as well as biomass.