Henry Head is the inner northern headland of Botany Bay, crowned by a complex of tunnels, forts and gun emplacements built in the 1880s against a feared Russian invasion, and the reef below it is one of the most colourful in the bay. Large boulders litter the sand while ledges, overhangs and swim-throughs abound, together with dozens of abandoned anchors from generations of fishing boats. The reef edge drops from 15–17 m near the anchorage to 23 m and deepens to 27 m towards the east where it meets the main shipping channel; several walls exist at different levels.

What sets it apart is the fixed life: McFadyen rates the sponges and sea squirts of many colours here among the best he has seen anywhere in Sydney, and the isolated boulders out on the sand are completely encrusted. The fish and critter list is long: groper, yellowtail, bream, old wife, mado, red and magpie morwong, black reef leatherjackets and schools of kingfish over the reef; common seadragons, red Indianfish, eastern blue devilfish, big-belly seahorses, pygmy pipehorses, moray eels, giant boarfish, nudibranchs and sea spiders on and under the rocks. Dived from an anchored boat the standard route follows the western reef edge at 23 m until it turns north and shallows, then returns through the overhangs; the alternative is a drift on the flood tide from the small point south of the concrete cliffs west to Bare Island, which McFadyen has done from shore.

It is the sheltered option when the north-easterly is blowing on a summer afternoon and unsuitable in a big southerly. Suitable for Open Water divers with a guide at the 15–18 m level and for advanced divers along the 23–27 m edge; Abyss, Pro Dive and Sydney Dive Academy all run it regularly.

Boat dive. From the Cooks River/Kyeemagh, Foreshore Road or Bonna Point ramps run to the northern side of the bay entrance, about 1 km east of Bare Island, 10–15 minutes from Kyeemagh; anchor in about 18 m at the GPS mark. Abyss, Pro Dive and Sydney Dive Academy boats visit regularly.

A shore drift is possible for fit divers: walk from the La Perouse loop through the national park to the small point south of the concrete cliff section, enter 60–90 minutes before high tide and drift west along the reef to Bare Island.

Henry Head's great virtue is that it is protected in north-easterly winds – the summer sea breeze that blows out the ocean sites – making it the classic hot summer afternoon dive; it is unsuitable in big southerly seas and winds, which push straight into the entrance. Tidal current runs along the reef and is used for the drift to Bare Island on the flood; on the ebb after rain the bay's dirty water reduces visibility, so dive high or incoming tide. The shipping channel into Port Botany passes just south of the reef edge – stay on the reef and ascend on the line.

Drop over the wall from the anchor to the reef edge at 23 m and follow the western reef edge past the isolated sponge-covered boulders; the reef turns north and shallows to 18 m at the turnaround (about 22 minutes). Return along the shallower wall through the overhangs and swim-throughs to the anchor, finishing on the 10–12 m reef top.

Abyss Scuba Diving, Pro Dive Coogee/Cronulla and Sydney Dive Academy run boat dives here regularly, often paired with Bare Island Deep Wall or Magic Point; Frog Dive and Dive Centre Bondi occasionally. St George Scuba Club by private boat.