Healthy coral populations in the reef and elsewhere in the Coral Sea were discovered below 100 feet -- deeper than scuba divers normally go -- and even as deep as 260 feet, the survey found.
"The Holmes and Flinders Reefs in the Coral Sea are renowned for having been badly damaged," deep reef survey leader Pim Bongaerts of the University of Queensland said.
Most of the damage to the shallower coral was caused in recent years by powerful cyclones.
"Yet we have found their deep reef zone is hardly disturbed at all. In fact the most striking thing is the abundance of coral on the deep reef," he said. "What has blown me away is to see that even 70 to 80 meters down (230 to 260 feet), there are significant coral populations."
The survey team used remotely operated vehicles able to reach depths of 330 feet, CNN reported Friday.
Deep-water reefs might be able to help the shallower ones recover, Bongaerts said.
"At the moment we know little about the extent of [coral] larval movements between the shallow and deep reef, but we are seeing species that exist in both zones," he said.