floating fern

Salvinia natans (commonly known as floating fern, floating watermoss, floating moss, or commercially, water butterfly wings) is an annual floating aquatic fern, which can appear superficially similar to moss. It is found throughout the world where there is plentiful standing fresh water, sunlight, and humid air, but is especially common in Africa, Asia, central Europe, and South America. In New York State and Massachusetts, it is an introduced species.