Diamond Reef has built its reputation in the Forster area almost entirely on macro life: local records put the nudibranch count here at 38 different varieties, an exceptional tally for a single site and a strong draw for underwater photographers and divers with a specific interest in these small, colourful sea slugs. The reef itself, at 16 to 20 metres, is described as carrying extensive soft and hard coral growth alongside sponges, providing the varied micro-habitats that support such a wide nudibranch range — different species tend to specialise on particular sponge or coral hosts, so a reef with this much variety in its sessile invertebrate cover naturally supports a correspondingly wide range of nudibranchs feeding on them. This makes Diamond Reef a natural complement to Forster's bigger-animal sites like The Pinnacle and Latitude Rock: where those dives are built around grey nurse sharks and turtles, Diamond Reef rewards a patient, close-focus approach and is best dived with a macro lens or a genuine willingness to spend the whole tank moving slowly and looking closely rather than covering ground.

It is a popular inclusion for repeat visitors and photography-focused groups, and Forster Dive Centre uses it as a deliberate change of pace from the area's shark and turtle sites. Divers unfamiliar with nudibranch identification will get more out of the site with a guide who knows where the resident species are currently sitting, since many are small and easily missed without local knowledge. Bring a torch even in daylight to pick out colour and detail in the shadier crevices where many of the smaller species congregate.

Boats depart from Forster Dive Centre's base at Tuncurry (30 Manning Lane) or the Forster/Tuncurry boat ramp on Wallis Lake, running out through the lake entrance to the open sites. Forster-side sites (Latitude Rock, The Pinnacle, Bennetts Head Bommie) are 10-25 minutes away; Seal Rocks sites are a longer run of roughly 45-60 minutes further south, or reached by launching a boat directly from the Seal Rocks/Sugarloaf Point boat ramp for a much shorter trip.

Forster and Seal Rocks sit on an open, exposed stretch of coast with limited shelter — trips are cancelled in significant easterly swell or strong wind, and operators generally want under 1.5-2 m swell to run safely, especially for the Seal Rocks sites given the longer, more exposed run. Visibility is typically best in autumn and winter (15-30 m) and can drop after East Coast Lows or heavy rain from the Wallis Lake/Myall Lakes catchments. Grey nurse sharks are present through most of the year with the largest aggregations typically reported over the cooler months.

Descend onto the reef at 16-20 m and adopt a slow, macro-focused pace, working ledges and sponge-covered surfaces methodically to find the site's exceptional range of nudibranch species, rather than covering the reef quickly.

Forster Dive Centre (Tuncurry) — daily boat trips to Forster and Seal Rocks sites, year-round.