Pond scum, typically
I believe the answer is:
algae
(Other definitions for algae that I've seen before include "Water plants seen in a gale" , "Scum" , "Marine growths" , "Aquatic growths" , "Simple organisms, e.g. seaweeds" .)
I believe the answer is:
algae
(Other definitions for algae that I've seen before include "Water plants seen in a gale" , "Scum" , "Marine growths" , "Aquatic growths" , "Simple organisms, e.g. seaweeds" .)