Gulf of Carpentaria was a big iron screw steamer of 2,434 tons, 88.3 m (290 ft) long, built by William Gray and Co at West Hartlepool in 1881 with a double bottom and six watertight compartments, one of the new generation of cargo liners on the England–Australia run. On 15 September 1885, outward bound for England under Captain Robert Thompson and steaming westward at full speed past Wilsons Promontory, she struck an uncharted rock in the Anser Group – a pinnacle only 40 m across rising to within 5 m of the surface – and went down head first in the deeper water beside it. No lives were lost.

The rock has been Carpentaria Rock ever since, and the wreck was never salvaged. She lies in 48–50 m at the foot of the pinnacle, mostly collapsed after 140 years of Bass Strait swell – nature, as the Scuba Doctor puts it, is reclaiming her – but the size of the ship means there is a great deal of iron: hull plating and frames, boilers and the engine, and the bow where she struck. Because the site is inside the Wilsons Promontory Marine National Park and far from any port, it is pristine: the wreck and the pinnacle are smothered in sponges, jewel anemones, sea whips and zoanthids, with schools of butterfly perch, boarfish, ling and big crayfish, and the Australian fur seals of Kanowna Island 1.2 km away frequently join divers.

Visibility of 20–30 m is normal. It is a decompression dive at the far end of a two-hour passage, restricted to slack water, and it is done a few times a year by Melbourne technical clubs and Prom expeditions. The great advantage over the deep Graveyard wrecks is the pinnacle itself, which allows the decompression to be done on a spectacular wall rather than hanging in blue water.

It suits technical divers who want a genuine expedition with an unsalvaged Victorian-era liner and world-class reef in the same dive.

Boat only and remote. The Anser Group lies off the south-western tip of Wilsons Promontory, 40–50 km by sea from Port Welshpool (the usual departure; Lewis Channel ramp and wharf, parking, toilets, fuel) or from Port Franklin, and roughly 30 km from Tidal River, which has no boat access. Drive Melbourne–Port Welshpool via the South Gippsland Highway, about 2 h 45 min.

Trips are organised by Melbourne technical clubs and the occasional Prom dive expedition, often camping overnight at Refuge Cove or Waterloo Bay to be on site at dawn slack. The rock itself is unmarked and only 40 m across – a sounder and the GPS mark are essential. Marine national park – no fishing or collecting.

The Anser Group sits in the tidal race between Wilsons Promontory and the Bass Strait islands, and the Scuba Doctor restricts the site to slack water flood or ebb (SWF, SWE) – outside slack the current over the pinnacle is unworkable. It is fully exposed to westerly and south-westerly swell wrapping around the Prom; a window needs swell under about 1.5 m and light winds, plus a benign forecast for the 2-hour passage, which in practice means a few days in autumn. Visibility is typically 15–30 m in the clean offshore water.

Fog is common in the same settled conditions.

At slack water, descend the shot beside Carpentaria Rock to the collapsed hull in 45–50 m, survey the bow (which went down head first into the deeper water beside the rock), the boilers and engine and the debris trail towards the pinnacle in 20 minutes, then ascend the pinnacle wall to decompress on the rock's 5 m summit out of the current.

Technical (decompression) dive. Normoxic trimix (e.g. 21/35 or 18/45) recommended; 20 min bottom time gives roughly 25–40 min of decompression on EAN50 and oxygen. Air dives to this depth are strongly discouraged.

Drop a weighted shot on the wreck, use a delayed SMB from the wreck or a decompression trapeze under the boat; the site is in a shipping approach so free-drifting deco is discouraged. Decompress on the pinnacle wall; slack water flood or ebb only.

No regular operator. Dived occasionally by Melbourne technical clubs and Prom dive expeditions from Port Welshpool, perhaps a few times a year in autumn; Wilsons Prom charter operators (e.g. from Port Welshpool) will run it by arrangement for qualified groups.