Tenth of June Deep is listed as a separate site by Lord Howe's tourism body, and it corresponds to the deep plateau and vertical walls Pro Dive describes at 24–36 m on the Tenth of June reef. It is dived as a deeper profile on the same structure, for divers who want more time on the walls and less on the pinnacle top.

The deeper part of the reef is where the Coral Sea influence is strongest. The walls carry black coral trees, gorgonian fans and extensive soft corals, and the tunnels and swim-throughs are the haunt of black cod, which grow very large here. Pro Dive's dive accounts from the Admiralty Islets mention steeper drop-offs and deeper plateaus drawing large pelagic fish – kingfish, large silver trevally and unicornfish – with long-snouted flutemouths up to a metre long and blue angelfish on the reef. The Lord Howe tricolour fairy basslet and Japanese boarfish are two of the local specialities to look for.

The dive is relatively short on bottom time because most of it is spent below 25 m, and the plan usually involves a direct descent to the plateau, a run along the wall and a gradual ascent up the pinnacle to use the shallower reef for off-gassing. Nitrox, where available, is worth using.

It suits experienced divers with deep training who are comfortable in current. In most respects it is the same site as Tenth of June, but it is worth separating for planning because the depth, current exposure and certification level are different. Operators choose it on calm days with the wind in the south or south-west, which shelters the Admiralty Islets.

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 directly to the deep plateau at about 24–30 m and follow the vertical walls, keeping a close eye on no-decompression time. Look for black coral trees, gorgonians and black cod in the tunnels, then ascend up the pinnacle to finish the dive and safety stop on its shallow top.

Nitrox recommended to extend no-decompression time; plan a gradual ascent profile up the pinnacle.

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.