The Dunbar is the most famous shipwreck in Sydney and one of the worst maritime disasters in Australian history. The three-masted clipper was built of British oak and East India teak by James Laing and Sons of Sunderland in 1853 for the shipowner Duncan Dunbar; at 61 m and about 1,300 tons she was the largest ship ever built in Sunderland and carried a copper rampant-lion figurehead. After service as a Crimean War troopship she began the London–Sydney run in 1856.

On the night of 20–21 August 1857, arriving from London with 63 passengers and 59 crew in a gale and driving rain, Captain James Green mistook the gap in the cliffs for the harbour entrance and drove the ship onto the rocks just south of The Gap. She broke up almost immediately. Of 122 aboard, 121 died; the sole survivor, able seaman James Johnson, was washed onto a ledge and hauled up the cliff 36 hours later.

The disaster led directly to the building of the Hornby Lighthouse on South Head. Scuba divers first worked the site in 1955 and much was taken in the 1950s and 1960s, including gold coins, pennies and trade tokens, before it was protected. What remains is a scatter of wreckage in a small inlet at the foot of the cliffs in 4–7 m.

The most obvious features are dozens of iron ballast blocks, sheets of copper sheathing from the hull, lengths of chain, pieces of mast and swing anchors, with two larger anchors lying north of the ballast field. In the crevices divers still see fragments of green, black, blue and clear bottle glass and pieces of decorated china. Kelp covers the site in many years and makes it hard to see the bottom, so the experience varies with the season.

Fish life is typical of the eastern cliffs – luderick, silver sweep, mado, eastern blue gropers and schools of yellowtail – and the cliff face towering above adds atmosphere. It is a shallow, contemplative heritage dive rather than a spectacular one, suited to divers interested in Sydney's history who are comfortable with some surge. It pairs naturally with The Gap reef dive nearby.

Boat only – the cliffs at The Gap are sheer and there is no safe shore access. Launch at Rose Bay (public ramp off New South Head Road) or leave from Watsons Bay/Rushcutters Bay, run out through the Heads and turn south; the inlet is just past The Gap lookout and before the next small point, 10–20 minutes from Rose Bay. Anchor well offshore in 10–15 m clear of the wash off the cliff and swim in on the surface or along the bottom to the ballast field in 4–7 m.

McFadyen's GPS is 33° 50.8988' S 151° 17.2812' E. Most divers do it as a second dive after The Gap or The Colours.

Needs absolutely flat seas. The site sits in 4–7 m right against the base of the South Head cliffs, so any easterly, north-easterly or southerly swell produces heavy surge and backwash that makes it undiveable and dangerous for the boat. Winter westerlies, which flatten the sea against the cliffs, give the best conditions; aim for swell under 1 m and a long period.

Visibility is best after several calm days and on the incoming tide, when clean ocean water replaces harbour runoff. Summer north-easterly sea breezes make the anchorage uncomfortable after midday. Kelp cover varies seasonally and hides much of the wreckage in some years.

Anchor offshore in 10–15 m, swim in to the inlet and search the bottom in 4–7 m for the iron ballast blocks and copper sheathing, then work north along the base of the cliff to the two anchors lying north of the ballast field. Move slowly and fan kelp aside gently to see small artefacts. Swim back out to the anchor for the ascent; keep well clear of the breaking wash line.

Protected historic shipwreck – no disturbance or removal of relics.

Dive Centre Bondi, Pro Dive Coogee and Frog Dive occasionally visit on dead-flat days as a shallow second dive after The Gap; otherwise private boats and clubs.