Gorgonia Grove is the stretch of inner North Head reef where the gorgonian sea fans that give the whole headland its reputation are at their most concentrated, growing on the sides and undersides of the boulders in fans a metre across, orange, red and white, with basket stars coiled in them by day and spread at night. Sydney Dive Charters lists it at 10–26 m and notes that it was 'recently altered by a rockslide, creating additional structure': a section of the sandstone cliff above collapsed into the water, and the fresh blocks now lie across the older reef, forming new walls, gaps and overhangs that are slowly being colonised. The dive therefore has two moods.

On the old reef the growth is mature – gorgonians, sea whips, sponges, soft corals and sea tulips packed on every shaded surface, with nudibranchs, cowries and decorator crabs among them – while on the new fall the rock is still pale and bare in places, an unusual chance to watch a Sydney reef being recolonised. The mobile life is the usual rich North Head cast: weedy sea dragons on the sand line at 22–26 m, wobbegongs, Port Jackson and crested horn sharks under the ledges, bull rays, blue groper, yellowtail and pomfret schools, giant cuttlefish and octopus in the cracks. The site faces the harbour and is sheltered from the north-easter; tidal current along the face is usually mild.

Its one particular caution is the rockfall itself – loose slabs should be treated with respect and not swum under. Gorgonia Grove suits Open Water and Advanced divers and above all photographers, for whom the fans with a diver silhouetted behind are the classic North Head image; it is inside the North Harbour Aquatic Reserve where nothing may be taken.

Boat only. Dive Centre Manly loads at Manly Cove beach beside the wharf; Pro Dive Manly and Sydney Dive Charters load at the Little Manly boat ramp (end of Stuart Street, Manly – free parking, set-up benches, toilets at the reserve); Sydney Dive Charters also picks up at Rose Bay public wharf. From Manly the run is 10–15 minutes across North Harbour to the inside of North Head, 20–25 minutes from Rose Bay.

Private boats launch at Little Manly, Roseville Bridge (Middle Harbour, 30 minutes) or Rose Bay. Boats anchor on the reef in 15–20 m or run in toward the cliff and drop the anchor when the bottom appears; there are no moorings, and many abandoned anchors litter the reef. The fresh pale scar of the rockslide on the cliff face marks the anchorage.

The inner face of North Head is the most sheltered ocean-quality diving in Sydney. It faces west-south-west into the harbour, so it is protected from the north-east sea breeze and from northerly and easterly swell, and is at its best when a strong north-easter is blowing and every ocean site is rough. It is exposed to southerly swell rolling through the Heads: a big southerly (over 2 m) sends surge along the cliff and dirties the water, though the deeper sponge gardens are usually still diveable.

Tidal current runs along the wall, east on the flood and west on the ebb, strong enough to plan a drift; slack water is easiest for novices. Visibility is 10–15 m on average, 25 m on winter westerlies, and drops after heavy rain when the harbour flushes brown. Ferry, shipping and small-boat traffic through the Heads is constant – ascend on the anchor line or a DSMB close to the cliff.

Descend to 18 m and work along the base of the new rockfall at 20–24 m where the freshly exposed faces and old sponge-covered boulders meet, then return through the gorgonian-covered ledges at 12–16 m. Keep clear of any loose or overhanging slabs. Ascend on the anchor line.

Sydney Dive Charters – North Head rotation of guided double dives; Dive Centre Manly and Pro Dive Manly dive the same stretch under the general North Head label.