Rupert's Reef is one of the Admiralty sites the island's tourism body lists by name, and it features in both Nigel Marsh's and Divernet's accounts of diving Lord Howe. It is a rocky pinnacle sitting in the channel between No-Name Rock and Roach Island, rising from about 24 m to a top at around 12 m. Marsh recorded 20 m visibility on his dive; on better days it is clearer.

The pinnacle is small enough to circle comfortably in one dive, and the channel position means fish are drawn to it. Marsh's species list reads like a summary of Lord Howe's mixed fauna: splendid hawkfish, Lord Howe butterflyfish, doubleheader wrasse, McCulloch's anemonefish, Cook's scorpionfish, painted morwong, damsels, sweetlips, lionfish, wrasses, leatherjackets, drummer, pufferfish, boxfish and a Galapagos shark. Several of those – the doubleheader and McCulloch's anemonefish in particular – are found only around Lord Howe and nearby reefs.

Divernet adds a resident green turtle, squat lobsters, grey coral gobies, saddled rock cod and painted crayfish, with small sea fans and purple and orange bryozoans colouring the rock. It is a good site for macro photography because the life is concentrated on a small structure, and the moderate depth allows a decent bottom time.

Conditions are those of the Admiralty Islets in general: sheltered in southerly weather and exposed to north-easterly swell, with possible current through the channel. It suits Open Water divers with some experience; a newly certified diver will be fine on a calm day with a guide. It pairs well with Roach Island or Deacon's Delight as a double.

Lord Howe is reached only by air: QantasLink flies from Sydney daily (about 1 h 50 min), with Brisbane and seasonal Port Macquarie services. Accommodation must be booked before flights (visitor numbers are capped at about 400) and the checked-baggage limit is 14 kg, so most divers hire gear on the island. Dive Lord Howe's shop is at 2 Lagoon Road beside the Lagoon Beach boatsheds; most lodges transfer divers or it is a short bike ride.

Divers board the boat, which is moored in the lagoon, and exit the lagoon through North Passage, then run north-east around North Head to the Admiralty Islets, a group of seven rocky islets a few hundred metres to about 1.5 km off the island's north-east tip. The trip takes about 20 minutes. The boat anchors on sand or a small reef close to the site or runs live if there is current.

Lord Howe sits in the path of the prevailing south-east to east trades and winter westerly fronts. The Admiralty Islets are exposed to north-east and easterly swell and to northerly winds, which blow them out; they come into their own in south-westerly to southerly winds, when the island shelters them and the southern and western sites are rough. A 1.5 m swell from the north-east makes the shallower gutters surgy, and a lump above about 2 m stops the trip.

The Coral Sea current washes these islets more than other sites, so currents can pick up, especially on the outer edges. Visibility is typically 30–40 m. Best months are February–May; winter westerlies are fine here if the swell is down.

Descend to the base of the pinnacle at around 20–24 m and circle it slowly, looking for painted crayfish and squat lobsters in the cracks and sea fans on the exposed faces. Spiral up to the 12 m top in the second half, where the resident green turtle and schooling fish are often found, and do the safety stop on the line.

Dive Lord Howe (PADI 5-star, 2 Lagoon Road) – morning double boat dives daily in season, afternoon single dives on demand; site chosen on the day by wind and swell. Howea Divers has also advertised dives here.