The vessel

The Tiwi Pearl is a 24.15 m steel fishing vessel built in the mid-1960s at Mobile, Alabama, on the Gulf coast of the United States. She is 6.64 m in maximum breadth, about 12 m from keel to highest point, and measured 96 t net and 157 t gross. By the time the Queensland Government acquired her she was described simply as an ex-tuna fishing vessel. A fire aboard had led to her being written off, and she was proposed for breaking up for scrap before the Moreton Bay artificial reef program took her instead.

That is the whole of her documented history. Where she was built for, who owned her, how she came to Australia and where the name Tiwi comes from are not recorded in any government material; see Gaps and uncertainties below.

The sinking, 12 March 2010

She was sunk by flooding rather than explosives. Naval architects were asked to draw up a flooding and venting plan so that she would go down under control and land upright. All machinery came out, and 32 t of concrete was pumped in to replace the weight. Four 100 mm pipes, each with a butterfly valve, were welded into the hull: three in the main engine room compartment and one in the freezer. The old diesel, fresh-water and live-bait tanks were filled with 85 t of seawater. She was held over the mark on a four-point anchor system, two lines forward and two aft, made fast to 500 kg clump weights with chain and wire rope.

On 12 March 2010 the four valves were opened by hand. About 350 t of seawater took roughly ten minutes to fill her compartments and put her on the bottom, standing perfectly upright with 8 m of clearance at low tide. Her position was fixed by sonar and GPS at 27°24.532'S 153°18.304'E (GDA94). Her large profile is what attracts the baitfish, and behind them the small tuna, mackerel and snapper the reef was built for.

Now the Harry Atkinson Artificial Reef

The Tiwi Pearl did not create the reef she lies on. The Harry Atkinson Artificial Reef is the oldest artificial reef in Moreton Bay, started in 1975 when more than 17,000 car tyres were dropped on the site over five years with the help of the Moreton Bay Trailer Boat Club at Manly, and topped up in 1987 with 200 shopping trolleys. Some of that material is still there and still holds fish; some has dispersed or been buried.

When Moreton Bay Marine Park was rezoned in 2009, recreational anglers lost access to some grounds. To partially offset that, the Queensland Government enhanced Harry Atkinson and built new reefs elsewhere in the bay: five others at the time of the Tiwi Pearl's sinking, eight in total today. The Tiwi Pearl was the major extension of Harry Atkinson. Around her, the site now holds:

YearMaterial
1975–80More than 17,000 car tyres, the original reef
1987200 shopping trolleys
Dec 2008150 m³ of quarried rock, giving small fish shelter
12 Mar 2010The Tiwi Pearl
Aug 2010450 t of clean concrete pipe donated by Humes, in four clusters of about 23 pipes each, 2.5–6 m high
Nov 2014A retired 26 m, 60 t Port of Brisbane barge, once a work barge for berth construction between Cairns and the Gold Coast and later a landing pontoon

Because the program's purpose is recreational fishing, the Director-General declared the 34 ha site a special activity area under the Marine Parks Regulation. The reef sits in a General Use zone, so line fishing and trolling are allowed (up to three lines and six hooks per person), charter fishing is allowed with a permit, and anchoring is allowed, with a permit needed to stay more than 14 consecutive days or 30 days in 60. Scuba diving, surface-supplied-air diving, snorkelling, spearfishing, dive charters and commercial fishing are all prohibited without a marine park permit or commercial activity agreement. The fact sheet puts it in one line: diving is not permitted on the Tiwi Pearl. Fines apply.

This entry exists so you know what is under you when you anchor over the wreck, and so you do not plan a dive on a hull you cannot legally dive. If you want a wreck to swim through in the bay, Curtin Artificial Reef off Moreton Island is the one built for divers. Turner Reef off Scarborough and the North Stradbroke Island reef are the two government reefs where recreational scuba is allowed.

If you fish it, fishing writer Kim Bain's advice on the Parks website is to fish the wrecks by targeting individual spots and moving on, and if you anchor, to be pinpoint accurate. The reef sits in current-swept open bay; heavy sinkers, the turn of the tide, and mid-week or after dark when the boat traffic drops off.

Positions

Position
Tiwi Pearl-27.40887, 153.30507
Quarry rock-27.40583, 153.31125
Pipe cluster 1-27.40437, 153.31173
Pipe cluster 2-27.40673, 153.30643
Pipe cluster 3-27.40895, 153.30878
Pipe cluster 4-27.41007, 153.30685

Declared special activity area, from the two gazetted notices (GDA94):

CornerPosition
NE-27.40335, 153.31233
E-27.40568, 153.31253
S-27.41090, 153.30688
W (2nd notice extension)-27.40915, 153.30352
NW-27.40617, 153.30597

The Tiwi Pearl position is the government's own fix. Rock and pipe positions are fishing marks published by third parties and have not been checked against the government map. Sound around before you anchor.

Gaps and uncertainties

  • Builder and original name. The fact sheet gives only "mid 1960s at Mobile, Alabama". No yard, launch name or official number has been found, so her US registry history is untraced.
  • Owners and the name. Nothing found on who owned her in Australia, when she arrived, or why she is called Tiwi Pearl. The name suggests a link to the Tiwi Islands or to pearling, but that is inference, not evidence.
  • Her working life and the fire. An earlier version of this note said she worked the Torres Strait pearl fishery, was converted for longlining out of Mooloolaba, and caught fire in June 2009. None of that appears in the fact sheet, the Parks website or any source found since, so it is recorded here as unverified rather than in the narrative above. The only documented facts are "ex-tuna fishing vessel" and "there was a fire aboard the vessel leading to its write-off".
  • Harry Atkinson. Who he was is not recorded in any government material on the reef, and none of the sources consulted say why it carries his name.
  • Heritage status. As a 2010 scuttling she is not in the Australasian Underwater Cultural Heritage Database and, being well under 75 years old, is not protected under the Underwater Cultural Heritage Act 2018. Her protection is the marine park special activity notice, not heritage law.

Further reading