Kanowna was a 6,993-ton, 126 m twin-screw passenger liner built by William Denny and Brothers at Dumbarton in 1902 for the Australasian United Steam Navigation Company's Sydney–Fremantle run, one of the finest coastal liners of her day. In August 1914 she carried a thousand men of the Australian Naval and Military Expeditionary Force towards German New Guinea, a voyage cut short by a stokers' mutiny over water rations in the heat of the boiler rooms; from June 1915 to 1919 she served as a hospital ship with 452 cots and 88 medical staff, making about ten voyages between Australia and England and bringing home the wounded of Gallipoli and the Western Front. Back in civilian service, she left Sydney for Melbourne in February 1929 and on the morning of 18 February, in fog, ran onto rocks near Cleft Island off Wilsons Promontory.

Passengers were taken off by the SS Mackarra; she was got off the rocks but her boilers failed, the crew abandoned her to the SS Dumosa and she sank the next morning. The inquiry blamed her master for insufficient caution in fog. Lost for 76 years, she was found on 23 April 2005 by four Melbourne technical divers about 50 km into Bass Strait in roughly 80 m, and identified on 8 May 2005 against the builder's drawings.

She lies on a sand bottom at 80–82 m, and although corroded and collapsing in places, her sections remain recognisable – the bow, the long line of the hull, the boilers and engines of a big twin-screw steamer, the stern – on a scale unmatched by anything else dived in Victoria. Visibility of 20–30 m is common and the wreck teems with ling, boarfish, butterfly perch and big crayfish; deep-water sponges and sea whips cover the steel. Kanowna is an expedition, not a charter: a 2–3 hour passage each way from Port Welshpool, 20 minutes at 80 m on hypoxic trimix or a rebreather, and an hour and a half of drifting decompression in the open Strait.

A few teams a year manage it. For Australian technical divers it sits alongside the Alert and the City of Rayville as the pinnacle of Victorian deep wreck diving, and it is the only one of the three that is neither in a protected zone nor requires a permit – though it is a historic shipwreck under Commonwealth law and nothing may be removed.

Expedition only. The wreck lies off the south-western tip of Wilsons Promontory near Cleft Island, a long open-water passage from any port: Port Welshpool (Lewis Channel ramp and wharf) is the usual departure, about 60–70 km and 2–3 hours in a fast expedition boat around the Prom; Port Franklin, Port Albert and, for larger vessels, Western Port (Flinders/Hastings) have also been used with an overnight anchorage at Refuge Cove or Waterloo Bay. Drive Melbourne–Port Welshpool via the South Gippsland Highway, about 2 h 45 min.

Trips are organised privately by technical teams (Southern Ocean Exploration, Melbourne rebreather groups) who charter a suitable vessel; there is no ramp, mooring or shore facility at the site and everything – gas, scrubber, support divers – must be carried.

This is the most exposed dive site in the state – the open Southern Ocean side of Wilsons Promontory, where the westerly swell wraps around the Prom and the tidal streams of Bass Strait run between the Anser Group and Cleft Island. A viable window needs a stationary high over the Strait with swell under about 1 m and wind under 10 knots for the whole day, plus a benign forecast for the long passage home; such windows come a few times a year, mostly in autumn. Currents at 80 m are moderate but variable and the 90-minute decompression is done drifting under a surface float with the boat following.

Fog, which sank the ship, is a real hazard in the same conditions. Visibility at depth is frequently 20–30 m, the best in Victorian wreck diving, because the site is far from any river.

Expedition CCR dive: descend the shot to the wreck (75–82 m), spend 20 minutes on the highest and most recognisable sections – the bow, the boilers and engine area, the stern – photographing and surveying, then leave the shot on a DSMB and complete 90–120 minutes of drifting decompression under the boat with support divers meeting the team at the 21 m and 6 m stops.

Expedition CCR dive: diluent around 10/60–10/70, bailout for a full 80 m ascent (typically 3–4 stages or team bailout), oxygen and EAN50 deco gases, drifting decompression under a float with support divers and a live boat. Open-circuit is impractical. Historic shipwreck – no artefact recovery.

No commercial operator. Found and dived by Southern Ocean Exploration (2005) and since visited by a small number of Melbourne closed-circuit rebreather expeditions, typically one or two attempts a year in the best autumn weather; Divernet describes it as one of the deepest historic wrecks regularly dived in Victoria, but 'regularly' here means a handful of dives annually.