The discovery comes after a study earlier this month found the Great Barrier Reef had lost more than half its coral in the last three decades.
Using the underwater robot known as SuBastian, the scientists filmed their exploration of the new reef, collecting marine samples on the way, which will be archived and placed in the Queensland Museum and the Museum of Tropical Queensland.
"To not only 3D map the reef in detail, but also visually see this discovery with SuBastian is incredible," Beaman added.
Although the northern section of the Great Barrier Reef suffered from bleaching in 2016, Beaman said this detached reef didn't display any evidence of damage.
Bleaching occurs when the water is too warm, forcing coral to expel living algae and causing it to calcify and turn white.
The Great Barrier Reef runs 2,300 km (1,429 miles) down Australia's northeast coast spanning an area half the size of Texas. It was world heritage listed in 1981 by UNESCO as the most extensive and spectacular coral reef ecosystem on the planet.