A mesophotic coral ecosystem at a depth of 70m in the Hawaiian island of Maui's Au'au Channel.
Such an ecosystem is the deepest of the light-dependent coral reef communities and is usually found 30m to 152m below the surface.
Scientists have discovered the largest recorded uninterrupted mesophotic coral ecosystem in the Au'au Channel, extending more than 7 sq km at about 48m to 91m deep and including areas of 100 per cent coral cover.
Coral cover refers to the proportion of reef surface covered by live stony coral instead of sponges, algae or other organisms.
The study, led by Bishop Museum in Hawaii and supported by the United States' National Oceanic and Atmospheric Administration (NOAA), was published recently in the scientific journal PeerJ.
Dr Richard Pyle, Bishop Museum scientist and lead author of the publication, said the waters off Maui present the perfect environment for these reefs.
"The area combines clear water, which allows light to reach the corals; good water flow enhancing food availability; shelter from major north and south swells; and a submerged terrace between the islands at the right depth."
Mesophotic coral ecosystems lie well beyond the limits of conventional scuba diving and are among the most poorly explored marine habitats on earth.