The base of the blade-like reef is 1.5km wide, then rises 500m to its shallowest depth of only 40m below the sea surface.

The expedition’s Principal Investigator Dr Tom Bridge said new technologies are leading to a greater understanding of Australia's marine environment.

“We know more about the surface of the moon than we know about what lies in the depths beyond our coastlines,” said Dr Bridge, also from the ARC Centre of Excellence for Coral Reef Studies at James Cook University.

"Combining mapping data and underwater imagery helps understand more about this newly discovered reef and its role within the Great Barrier Reef World Heritage Area.”

Co-founder of Schmidt Ocean Institute Wendy Schmidt agreed the unexpected discovery shows there are still many unknown structures and species within our oceans.

“The state of our knowledge about what’s in the ocean has long been so limited,” Ms Schmidt said.

“(But) thanks to new technologies that work as our eyes, ears and hands in the deep ocean, we have the capacity to explore like never before.

"New oceanscapes are opening to us, revealing the ecosystems and diverse life forms that share the planet with us.”

The new discovery adds to the seven other tall detached reefs in the area – all mapped in the late 1800s. 

The collection includes the reef at Raine Island, which is the world’s most important green sea turtle nesting area.

The Falkor is currently on a 12 month exploration of the ocean surrounding Australia, due to end in mid-November. 

WATCH A FLY-THROUGH VIDEO MAPPING THE DISCOVERY BELOW: