Cape Nelson is the basalt headland 11 km south-west of Portland, crowned by the 1884 lighthouse and protected on land as Cape Nelson State Park, and it is the most dramatic diving coast in the far west of Victoria. The Scuba Doctor's Cape Nelson Lighthouse entry is a collective one covering a large number of different dive sites around the cape, from 6 to 36 m, and names a few: Capper's Camp at 5–14 m, Yellow Rock at 5–10 m and Devils Kitchen 1.4 km to the east-north-east, with Flat Rock, the Isabella wreck and Jones Bay recorded separately along the same shore. Visit Portland adds that there are two unidentified wrecks in the area and habitats ranging from sand to kelp forest. The cape's cliffs continue underwater as basalt walls, ledges and boulder slopes dropping steeply into cold, clear water, and the growth on them is the richest on the Portland coast: sponges, ascidians, bryozoans and gorgonians in the shade, kelp on the tops. The Scuba Doctor lists seaweed, catsharks, shrimp, cuttlefish, octopus, nudibranchs, banded morwong, sea sweep, magpie perch, leatherjackets and wrasse, and abalone and crayfish are taken here. Seals from Cape Bridgewater pass along the cape and blue whales feed offshore in the upwelling season.

It is boat diving first and foremost – a long, exposed run from Portland Harbour with the sounder as the guide to structure – and Advanced in the sense that the good sites are deep and the whole cape is exposed. A few shore entries exist, reached by steep clifftop walks with ladders and ropes, and they are for fit, experienced divers on flat days only. No dive charter operates from Portland, so the cape is dived by private boats and by arrangement with fishing charters, and it is correspondingly little known; Portland SCUBA is the source of local advice. For a group with a good boat on an autumn high it offers wall diving to 36 m under a lighthouse on one of the wildest capes in Australia.

Boats launch at the Portland Harbour ramps on Lee Breakwater Road (North Ramp and South Ramp), both with trailer parking, inside the harbour breakwaters. From the harbour run south-west around Point Danger and along the coast to Cape Nelson, about 15 km and 30–40 minutes; the Scuba Doctor advises using the sounder to find structure below the cliffs. By land, Cape Nelson Road (C192) runs 11 km from Portland to the lighthouse and Cape Nelson State Park; a handful of shore entries such as Capper's Camp are reached by steep tracks and, in Visit Portland's words, ladders or rope work, and are for the fit and experienced only.

Portland SCUBA in town has air and local knowledge.

Cape Nelson is a fully exposed basalt headland in the open Southern Ocean and its reefs are best dived, in the Scuba Doctor's words, in good conditions with a low swell and light offshore winds. The eastern side (Flat Rock, Capper's Camp) is sheltered in westerly weather and the western side (Jones Bay) in easterlies; the cape itself needs swell under about 1 m and a northerly. Yellow Rock is very exposed to southerly swell and is ordinarily a surf beach.

The long run from Portland means a forecast that holds all day. The Bonney Upwelling brings cold, sometimes green water from November to April and autumn is clearest. Shore entries are only for flat calm.

Anchor on sand at the base of the cliff in 18–25 m, descend the line and follow the basalt wall and boulder slope with the cliff on one side, exploring the ledges and gutters where the crays and morwong sit, then work up the wall toward the kelp zone at 8–12 m for the second half of the dive. Turn at a third of your gas and return to the anchor for a 3-minute stop; on the deeper sites to 30–36 m keep bottom time short.

Deeper sites to 30–36 m suit EAN28–32 with short bottom times; no formal deco diving documented.

No dedicated dive charter operates from Portland. Portland SCUBA (PADI centre) runs courses and occasional day trips; local fishing charters take divers by arrangement; Portland dive club members use private boats. Warrnambool Diving visits occasionally.