JOHANNESBURG - Watercan is concerned about a deluge of water lettuce in the Vaal River.
The alien plant species is a threat to aquatic life and its leaves are often poisonous.
The non-profit organisation says something must be done urgently to address it.
Executive Manager Ferrial Adam said these plants reproduce very quickly if the environment is conducive to that.
WATCH: SA's water crisis | Invasive plants taking over Vaal River
"The thing about the water lettuce, it wasn't in the Vaal area," she said.
"But since 2021, the organisations that have been working there have been doing really good advocacy and activism to create awareness."
She said the challenge is that if you leave it, it has the potential to take over.
"Then you'll have this carpet of lettuce which blocks sunlight into the water, takes out the oxygen from the water which affects basic ecosystems."