common hornwort (Ceratophyllum demersum); Analipus japonicus (species of brown alga)
scraps of seaweed; death at sea (metaphor)
hydrilla (species of aquatic plant, Hydrilla verticillata); Papenfussiella kuromo (species of brown algae)
seaweed salt; salt from burning seaweed
Closterium (genus of algae)
seaweed bed; seaweed forest
Eurasian water milfoil (Myriophyllum spicatum); aquatic plants such as hornwort that are commonly used in goldfish tanks, etc.
waterweed (any aquatic plant of genus Elodea, esp. common waterweed, Elodea canadensis)
washed-up seaweed; stranded seaweed