The reef slope is the subtidal portion of the reef, extending from the reef crest or platform to the inter-reefal floor, which around Heron ranges from 10-25m. The reef slope varies depending on location but is typified by dense coral growth and diversity. In places, the reef is gently sloping, with branching and massive corals dominating. In other areas, the slope forms a steeper spur-and-groove structure that is typified by plate and massive corals. The under-surfaces of coral in the shallow part of the slope (less than 8m) are often populated by the same range of cryptic sessiles that are found on the reef flat and crest (i.e. ascidians, sponges and bryozoans). In the deeper part of the slope the species assemblages tend to change.