In towns across France, people woke up to their rivers beaming with a weird green glow on Monday, April 25. But this isn’t a belated St Patrick’s Day celebration or some "Simpsons"-esque radioactive gloop.

The rivers in 12 separate locations of France were dyed by Agents Environmental , an environmentalist group, who used the eye-grabbing color to display how easily and how far water pollution can spread.

“We used a colorant called fluorescein that’s totally harmless,” Yannick Pognart, environmental inspector and activist, told Le Local News. “It’s to show the path pollution takes in the water. It’s a strong visual, but it’s completely safe. The fish don’t even notice.”

Fluorescein is an organic compound that is commonly used to trace the flow of water and has many applications in the field of biomedical healthcare.

The fluorescein dye is harmless. Agents Environmental

The stunt coincides with France's domestic environment conferences, which started this week in Paris. These conferences come quickly on the tail of 174 nations signing the COP21 Paris Agreement on Friday, April 22.

The group also wanted to highlight the lack of funding and resources available to public services to address environmental issues.

“Right now, the environment is very 'à la mode', everyone knows the consequences and that it’s something very important,” Pognart added. “On the other hand, we have more and more missions and less and less means to accomplish these missions.”