Marine researchers have discovered a coral reef more than three kilometers long off the coast of Tahiti in the depths of the South Pacific.
The structure formed by cnidarians is at a depth of 35 to 70 meters and appears to be in good condition, the journal New Scientist reported on Thursday.
It is one of the largest reefs discovered at this depth, the BBC said, citing the UN scientific organization Unesco, which led the mission.
Divers discovered the reef in November during an expedition off French Polynesia that is part of an international mission to map the seabed.
"It was magical to see huge, beautiful, rose-shaped corals stretching as far as the eye can see," said French photographer Alexis Rosenfeld, who led the international diving team.
It was "like a work of art".
In the coming months, scientists want to find out which species live around the reef.
There are probably many more of these ecosystems that we know nothing about, said Julian Barbiere from Unesco.
According to the UN agency, only about 20 percent of the seabed has been mapped so far.
Experts have been calling for measures to prevent the global coral reefs from dying off for a long time.
The main reasons for the destruction of coral reefs are overfishing, pollution of the seas and climate change.
Climate change is causing sea temperatures to rise, which in turn leads to the notorious bleaching of corals.