A 1.56km rose coral colony has been discovered in waters off the Cocos (Keeling) Islands.
While local divers have seen different parts over decades, researchers were stunned by the coral formation's actual size.
Researchers will use DNA to determine if the colony is made up of one organism or many genetically distinct individuals.
A kilometre-long coral formation thriving in waters off Australia's most remote inhabited territory is one of the largest ever recorded.
The 1.56km rose coral colony was discovered off the coast of the Cocos (Keeling) Islands.
For comparison, the colony covers the equivalent of approximately 100 buses laid end to end and an area three times the size of the Melbourne Cricket Ground.
Local divers have seen parts of the colony over decades, but a team of researchers formally mapped and examined the formation only in recent months.
Adelaide University marine biologist JP Hobbs said the research team initially began with a tape measure, before switching to GPS tracking when the colony's size became apparent.
"We first started running out measuring tapes and measuring it centimetre by centimetre," he said.
Dr Hobbs was alerted to the mega coral by Cocos-based dive operator Dieter Gerhard.
"He had seen this coral at a few of his dive sites," he said.
