The mysterious appearance of marble-sized balls along parts of the Australian coastline forced Sydney officials to close nine of its beaches in the Northern Beaches Council area earlier this week, while investigations into what they are and what had caused them are carried out.

The debris – said to be a combination of white and grey in colour – appeared along the shoreline in the city’s Northern Beaches area on Tuesday morning, when the occurrence was first reported from Dee Why Beach. 

As the day progressed, lifeguards from the Sydney Northern Beaches Council began to log reports of similar ball-shaped debris along the shores of Manly, Long Reef, Queenscliff, Freshwater, North and South Curl Curl, North Steyne, and North Narrabeen beaches.

It’s not currently clear what has caused the appearance of the debris or, indeed, what they contain. Nonetheless, the Northern Beaches Council was quick to close the nine spots at which they appeared and organised for the debris to be removed. According to an update issued by the Council this morning, most of these beaches have since been re-opened to the public. Officials are, however, still inspecting other beaches in the areas as a precaution while samples have been collected for testing.

The Mayor of the Northern Beaches Council, Sue Heins told Australian media at the time that “at the moment, we’re trying to keep everybody as safe as possible, keep them off the beach”. She added that while the Council has its theories as to what these debris balls are and what caused them, until officials receive the analysis results “we don’t know 100 per cent what they are”.

It all echoes of a similar occurrence in October 2024, when hundreds of black, marble-sized balls of debris washed up along the Eastern suburbs. After testing, these were found to consist mostly of fatty acids and petroleum hydrocarbons. The same analysis, however, failed to determine a source or identify what had caused them to form, owing to the fact – the council stated – that there were “no source samples available for comparison”.

With mystery and intrigue still hanging over the latest appearance, members of the public have been advised not to touch the debris balls found along Sydney’s north coastline this week.

At the point of closure of the nine Sydney beaches, the public were also advised to avoid the areas until the clean-up and investigation process – organised by Northern Beaches Council in collaboration with the NSW Environment Protection Agency – had been completed.

In an update issued Wednesday morning, most of the beaches have now been re-opened to the public. Only Dee Why Beach remains closed as council teams continue to clean the area.

Mayor Heins has congratulated crews for a swiftly organised beach clean that has allowed the council to re-open the areas to the public as quickly as possible, adding that officials will “continue to monitor the beaches conditions, especially following the high tide this morning”.

This is the third occurrence of its kind. In November last year, similar debris balls again washed up, this time along Bombo Beach, Kiama. They were found to have a similar composition to the debris balls found the month prior. The Environment Protection Agency is still awaiting the final results of tests on balls that washed up on Silver Beach in Kurnell in December.

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