A rare display of bioluminescence has illuminated waterways in Sydney’s northern suburbs, turning the dark nocturnal waters of Cockle Creek into a vivid display of blue light.

The image below shows bioluminescence captured in Cockle Creek, which flows through Bobbin Head and feeds Cowan Creek, which is a tributary of the Hawkesbury River.

Image: Bioluminescence in the Cockle Creek in August 2024. Source: @the25thfram / Instagram

Bioluminescence is a natural phenomenon which occurs when light is produced by a chemical reaction inside living organisms. It can occur in fish, squids, crustaceans and algae, and is typically triggered when the water these organisms are living in becomes disturbed or agitated.

These displays of bioluminescence can happen at any time of year and in waterways across Australia, including creeks, rivers and beaches.

Photographers captured bioluminescence at Lavendar Bay in late-November 2021, with the blue light adding to the luminous backdrop of the Harbour Bridge reflecting off Sydney Harbour. Bioluminescence also occurred in Tasmania in February of 2021 and 2023, and at Jervis Bay, NSW in June 2020.

Image: Bioluminescence at Lavendar Bay, NSW in November 2021. Source: @ryan_shanz / Instagram

Image: Bioluminescence at Cornelian Bay, Tas in February 2021. Source: @captchathemoment / Instagram

Image: Bioluminescence under the Aurora Australis at South Arm, Tas in February 2021. Source: @mantisalive / Instagram

Image: Bioluminescence at Bobbin Head, NSW in February 2021. Source: @the25thframe / Instagram

Tasmania Geographic has put together some useful tips on how to photograph this spectacular phenomenon if you are ever lucky enough to stumble across a bioluminescence display.