Surveyed 18 February 2017.
The first flank of Reef 20-104 is partly exposed to the prevailing wind and sea conditions found within the lagoon of the Great Barrier Reef. Manta tow surveys were conducted on the reef slope. The reef slope is generally vertical dropping off to a variable sloping reef base composed mainly of sand, reef framework and hard coral. The reef structure has many features including continuous wall, caves, swim throughs and overhangs.
The benthic community was dominated by hard coral, but coralline/turf algae was also common. Hard coral cover on the reef first flank was high composed mainly of Acropora species. The dominant coral lifeform was tabulate, but other forms such as digitate and branching corals were also present in decreasing order of abundance. Coral bleaching was present on a few individual colonies.
The fish abundance on the first flank of Reef 20-104 was very high. Conspicuous groups of reef fishes included fusiliers, surgeonfish, damselfish and baitfish. No crown-of-thorns starfish were observed on the first flank of Reef 20-104 . White syndromes (such as white band disease or shutdown reaction) were present on hard corals.