South Island is one of three Admiralty sites Diveplanit names in its survey of the islets, alongside the Tenth of June bommie and Roach Island. Diveplanit gives a combined profile for these sites – a top around 18 m, a median of 22 m and a bottom around 30 m – and describes steep drop-offs presented as walls of coral, bommies and large boulders, with swim-throughs where the islets meet below the surface.

The survey's species list gives a good idea of what to expect: tasselled flathead lying on the boulders, mosaic morays in the cracks, black-and-white lionfish including juveniles, dusky hydroids and gorgonian fans on the wall, blue nudibranchs and painted morwong. Diveplanit classes the Admiralty sites as wall and scenic reef dives with macro interest and occasional mega fauna, and Galapagos sharks, kingfish and trevally are the usual larger visitors.

As its name suggests, South Island lies at the southern end of the group, closest to Lord Howe itself. That position may give it more shelter than the outer islets in some conditions, but its exact location and the usual dive route are not published, so the coordinates are left blank. Operators choose among the Admiralty sites on the day according to wind and swell, and all of them are sheltered in southerly weather and exposed in north-easterlies.

It suits Open Water divers with some experience on calm days, and Advanced divers if the wall is dived below 20 m. The mix of coral walls, boulders and macro life makes it a good all-round dive, and it is about 20 minutes from the lagoon by boat.

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 the anchor line to about 18–20 m and follow the drop-off along the islet, looking at gorgonian fans and nudibranchs on the wall and morays and flathead in the boulders. Turn at half air and return shallower to the anchor for the safety stop.

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.