Dive after dive, marine researcher JP Hobbs followed an enormous expanse of coral along the underwater slopes of the Cocos (Keeling) Islands in the Indian Ocean. Each time he ran out of air before reaching its end, he marked his position and returned to continue mapping.
After 12 dives, the team had traced a formation extending 1.56 kilometers (0.97 miles) — roughly the length of 100 buses parked end to end.
It is one of the largest coral formations ever documented. But there’s an even stranger question: could all of it be one living organism?
The big boy coral
The formation consists of rose coral (Pachyseris), a genus known for its distinctive layered, ridged structures. It stretches across depths ranging from 14 to 65 meters (46 to 213 feet).
According to the Queensland Museum’s announcement, the formation averages 36.5 meters (120 feet) wide and covers approximately 56,940 square meters — nearly 5.7 hectares, or about eight soccer fields.
And that’s just what was mapped, it might extend even farther. Researchers identified additional sections another 200 to 300 meters beyond the main formation.
The coral wasn’t exactly a new find. Local dive operator Dieter Gerhard first noticed extensive stretches of it more than 30 years ago. But nobody had established just how far they reached.
Hobbs, from Adelaide University, worked with scientists from Queensland Museum and James Cook University to map the formation over several months. He used GPS to track his progress between dives.
Only after 12 dives did the researchers establish its extraordinary extent.
Is it one animal or a thousand?
This is where things get funky.
Corals are animals. They might resemble underwater plants or rocks, but they’re animals. Each colony consists of tiny creatures called polyps, which build hard calcium carbonate skeletons around themselves.
A colony can begin with a single polyp that reproduces asexually, creating genetically identical copies. Over time, those polyps can build an enormous interconnected structure.
In principle, a single coral organism could therefore contain millions of polyps.
But appearances can deceive, especially when it comes to corals.
Separate coral colonies can grow alongside one another until they appear continuous. Some can even fuse. In fact, researchers have documented naturally occurring coral chimeras — colonies containing tissues from genetically distinct individuals.
So where does this leave our Cocos coral?
The formation might be one enormous genetic individual. It might consist of numerous separate colonies growing together. Or it could be a more complicated mixture of fused colonies.
Researchers are now conducting genetic tests to distinguish between these possibilities.
For now, it’s just not clear yet.
Not the only stunning coral in the news
Remarkably, several corals have made headlines recently.
In November 2024, a National Geographic expedition discovered a massive Pavona clavus coral in the Solomon Islands, measuring approximately 34 by 32 meters. Scientists estimated that it was around 300 years old.
Then, in February 2026, a mother-and-daughter team of citizen scientists documented an even larger formation on Australia’s Great Barrier Reef.
That coral stretched 111 meters and covered almost 4,000 square meters. Its discovery raised similar questions about whether the structure represented one genetic individual.
The Cocos coral formation covers roughly 14 times that area, although researchers have not yet established whether the two formations are biologically comparable.
These discoveries suggest that some extraordinary coral structures may have been hiding in plain sight, overlooked because researchers had never systematically mapped their full extent.
They also raise another question: how do these giants survive?
Coral reefs face growing pressure from warming oceans. According to NOAA, approximately 84.4% of the world’s coral reef area experienced bleaching-level heat stress during the global event that began in 2023.
Some giant colonies may occupy relatively sheltered environments, although deeper water doesn’t necessarily protect corals from extreme temperatures.
For the Cocos formation, scientists have yet to establish its age, long-term health, or history of bleaching.
And perhaps its most intriguing secret remains unresolved.
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