Surveyed 19 April 2013.
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 steep sloping reef base composed mainly of sand, rubble and reef framework. The reef structure has many features including gullies, bommies, overhangs, caves and swim throughs.
The benthic community was dominated by coralline/turf algae, but hard coral was also common. Hard coral cover on the reef first flank was moderate composed mainly of Acropora species. The dominant coral lifeform was tabulate, but other forms such as digitate, sub-massive, encrusting and branching corals were also present in decreasing order of abundance. Coral bleaching was not present.
The fish abundance on the first flank of Reef 20-104 was very high. Conspicuous groups of reef fishes included fusiliers, baitfish and damselfish. No crown-of-thorns starfish were observed on the first flank of Reef 20-104 .