Buchanan's Wall lies at the southern end of South Solitary Island, dropping down the south-western face of a rock mass from about 15 m to 30 m, and stands apart from most of the other named sites in the group by being valued specifically for its invertebrate life rather than for sharks, rays or schooling fish. The wall itself is unremarkable in scale compared with Manta Arch's boulders or the Gantry's wreckage, but the encrusting growth along its face is exceptional, making this the site most photographers and macro enthusiasts request when visiting South Solitary Island. Nudibranchs in considerable variety cover the wall, alongside the more dramatic Spanish dancer — a large, flame-coloured nudibranch that swims in open water when disturbed — and thick growths of encrusting soft corals and anemones hosting resident clownfish populations.

Grey nurse sharks are occasionally reported cruising past the wall as they move between the more established aggregation sites further along the island, giving divers focused on macro subjects the occasional larger surprise as well. Depth and exposure put Buchanan's Wall a step up in difficulty from the boulder walls on the island's sheltered side: with a working depth of 15-30 m and moderate current typical of the southern end of South Solitary Island, this is recommended for Advanced Open Water divers with reasonable buoyancy control, both for their own safety and to avoid damaging the delicate invertebrate growth that makes the site worth visiting in the first place. On a calm day with good visibility, though, this wall offers some of the richest close-up subject matter anywhere in the Solitary Islands Marine Park.

Jetty Dive Centre departs from a public floating pontoon wharf on the Coffs Harbour boat harbour, opposite the Attitude Burgers building — check in first at 398 Harbour Drive, Coffs Harbour. It is roughly a 30-40 minute run out to South Solitary Island, 8 km offshore, in the dive centre's RIBs. Private boats launch at the Coffs Harbour public boat ramp inside the breakwall and follow the same course out past the harbour entrance.

South Solitary Island sits in open water 8 km off Coffs Harbour and is exposed to swell from the north-east through south-east; Jetty Dive Centre generally wants under about 1.5-2 m swell to run the outer moorings comfortably, switching to the more sheltered Split Solitary Island (only 20 minutes out) on rougher days. Visibility here is usually the best in the marine park given the distance from any river mouth, and the site's position at the boundary of tropical and temperate water means conditions can change quickly with wind shift. Summer (Nov-Apr) water is warmed by the East Australian Current to up to 26°C, bringing tropical fish, manta rays and, from December, leopard sharks; winter (May-Oct) cools to about 18°C but often gives calmer seas, giant cuttlefish and the peak grey nurse shark season (Jun-Nov, sometimes 30-60+ sharks on Manta Arch).

Humpback whales migrate past between April and November, peaking June-August northbound and September-November southbound. Currents can run strongly on the exposed north-eastern moorings (Manta Arch, Shark Gutters) and are much gentler on the sheltered north-western wall.

Descend the mooring to about 15 m at the top of the wall, work slowly down the face to 25-30 m examining the invertebrate growth for nudibranchs and Spanish dancers, and ascend along the wall for a multi-level profile and safety stop.

Jetty Dive Centre (Coffs Harbour) runs South Solitary Island most days conditions allow, typically a double boat dive; it is the flagship site for the only major dive operator based in Coffs Harbour.