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 into public rock pools at a popular Sydney beach.

What is believed to be a natural fluorescent dye, fluorescein, was spotted spreading through the rockpools at Cronulla, in Sydney’s south, on Friday with its origins still uncertain.

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

Many locals said they wouldn’t swim until the chemical dissipates, which takes between five to seven days as it’s naturally degraded through exposure to sunlight.

‘We believe the discolouration is likely to be fluorescein dye, which is commonly used in plumbing/drain testing and dissipates quickly once diluted,’ a spokesperson for the New South Wales Environmental Protection Agency said.

The agency also assured that the dye has a low toxicity but should be used minimally as ‘even small amounts can be highly visual’. 

‘Anyone concerned about possible water pollution should contact the Environment Line on 131 555 as soon as possible to ensure their concerns can be investigated promptly,’ the spokesperson for the agency said. 

An Australian dye manufacturer, Tintex, describes it as a ‘water colourant used to locate leaks in plumbing, tracing pipe locations, detect drain damage and water pathways’. 

‘It is non-toxic to the environment and odourless,’ the company’s website reads.

However, a safety data report from Tintex also warns to ‘not let this chemical enter the environment’.

Social media users were quick to point out the dye was mostly ‘harmless’ after photos of the rockpools were posted to a locals’ Facebook page.

One user claimed the dye is ‘legal to use in stormwater drain’.

‘Doesn’t look good whatever it is,’ another user responded, while other cautious users refused to swim in the area until the dye dissipated.

The colour is believed to be caused by a non-toxic, natural chemical called fluorescein that takes five to seven days to degrade through exposure to sunlight

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

A similar event occurred in Melbourne’s CBD on Thursday when a section of the Yarra River was dyed by fluorescein.

It is believed the dye had made its way into the river from a drain on nearby Elizabeth Street before dissipating shortly after. 

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

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

They also confirmed the results of their analysis had ‘not shown the presence of toxic elements’, reassuring perplexed residents and tourists.