North Rock is described by Divernet as a slightly deeper dive with a wall structure and tunnels and cracks running through the fringing reef. It is also noted as slightly more exposed than the inner sites and liable to small swell, which suits its name and position at the northern edge of the island's dive area.

The tunnels and cracks are the main structural feature. They cut through the fringing reef and give a sheltered path through the rock, with light coming in from above and at the ends. Black coral trees grow on the wall, which is typical of deeper, current-swept rock at Lord Howe.

The fish life is more pelagic than on the inner sites. Divernet lists Galapagos whalers, spangled emperor, sweep, kingfish and trevally. Spangled emperor form large schools at Lord Howe – Pro Dive recorded about 30 together at Gower Pinnacle – and kingfish grow large here because fishing pressure is low.

Because of the exposure and the depth, North Rock is best suited to Advanced divers. Small swell can make the tunnels surgy, so they should be entered only when the guide judges conditions right. It is dived when the wind is southerly and the north-east swell is down. The exact position is not published; the coordinates here are approximate. It is a good choice for divers who have done the sheltered reefs and want something with more of an open-ocean feel without the long run to Balls Pyramid. Visibility at Lord Howe's outer sites is usually 30 m or more, which shows off the wall and the schooling fish to good effect.

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 wall and follow it with the reef on one shoulder, entering the tunnels and cracks through the fringing reef where the guide leads. Look out for Galapagos whalers and kingfish along the edge. Turn at half air and ascend along the reef, doing 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.