The water in a fountain and nearby lake at Melbourne's Carlton Gardens have turned a deathly shade of red.
On Friday morning it was discovered that the iconic Hochgurtel Fountain in front of the Melbourne Exhibition Centre was spewing blood-coloured water.
A Melbourne City Council spokeswoman said the dyed water was "non-toxic" and therefore thought not to pose a danger to local plants and animals.
This is lucky for the ducks who, unperturbed by the change of scenery, were photographed paddling through the crimson lake.
"Remediation works are currently underway to drain the fountain and the lake," the spokeswoman said.
"They should both return to their normal colouring by tomorrow."
There has been speculation the prank could be the work of University of Melbourne students taking part in this weekend's Prosh Week celebrations.
The incident has been reported to Victoria Police.
The suspected prank harks back to startling photos that recently emerged of the Daldykan river in far north in Russia, transformed a dark shade of red.
The colour change there was later traced back to a spillage at a local metals plant.
A lake in Carlton Gardens has turned red after "non-toxic food dye" was dumped in the water in a suspected prank. #9News pic.twitter.com/YH3tcp8cbr
— Nine News Melbourne (@9NewsMelb) September 23, 2016
Someone's turned the lake in Carlton Gardens red with food dye... surely a Prosh Week prank? It has all the hallmarks! @uommedia pic.twitter.com/JjnWzdBraI
— Tom Kelly (@tpwkelly) September 23, 2016