Cronulla beach Sydney: Mystery over cause of fluorescent green water flooding into rock pools

Mysterious fluorescent green water has been spotted pouring out of a pipe and flowing into public rock pools at a popular Sydney beach.

What is believed to be a natural fluorescent dye, fluorescein, was seen on Friday spreading through the rock pools near Cronulla, in southern Sydney, the origin of which is still uncertain.

The dye has a myriad of uses, but is often used as a tracer to help experts track water flow and identify leaks in a water system.

Many locals said they wouldn’t swim until the chemical has dissipated, which takes five to seven days because it breaks down naturally with exposure to sunlight.

“We think the discoloration is likely due to fluorescein, a dye commonly used in pipe and drain testing that dissipates quickly when diluted,” said a spokesman for the New South Wales Environmental Protection Agency.

The agency also assured that the dye is of low toxicity but should be used minimally, as “even small amounts can be very visual.”

“Anyone concerned about potential water contamination should contact the environmental hotline on 131 555 as soon as possible to ensure that their concerns can be promptly investigated,” the agency spokesman said.

An Australian dye manufacturer, Tintex, describes it as a “watercolor agent used to detect leaks in pipes, trace pipe locations, detect runoff damage and waterways.”

“It is non-toxic to the environment and odorless,” the company’s website reads.

However, a Tintex safety report also warns not to “let this chemical enter the environment.”

Social media users were quick to point out that the dye was largely “harmless” after photos of the rock pools were posted on a local Facebook page.

One user claimed that the dye is “legal to use in rainwater runoff.”

“Doesn’t look good, whatever it is,” another user replied, while other cautious users refused to swim in the area until the dye wore off.

The color is believed to be caused by a non-toxic, natural chemical called fluorescein, which takes five to seven days to break down with exposure to sunlight

The chemical had tourists and locals in Venice, Italy, scratching their heads after one of the city’s famous canals turned bright green on May 28 (pictured)

A similar event occurred in Melbourne’s CBD on Thursday, when part of the Yarra River was dyed with fluorescein.

It is believed that the dye had entered the river from a drain on nearby Elizabeth Street, before disappearing shortly afterwards.

Just over a week earlier, locals and tourists in Venice were left scratching their heads after one of the city’s famous canals was turned bright green by the chemical.

The Regional Agency for Environmental Prevention and Protection of Veneto, a region of Italy that includes Venice, said fluorescein had turned up in samples taken.

They also confirmed that the results of their analysis had “not shown the presence of toxic elements,” reassuring bewildered residents and tourists.