The Cementco is the main wreck dive on the northern Moreton sites and a good contrast to the coral of nearby Flinders Reef. The ship had a varied life. Brisbane Scuba records her as commissioned by the Australian Army in 1944 as Crusader 2, and marinelife.org.au describes her as a 200 ft, roughly 500-tonne amphibious support vessel with six vehicle ramps, used to bring army equipment back from New Guinea after the war.

Sold in 1947, she spent decades working for Queensland Cement and Lime, carrying dead coral and sand dredged from Moreton Bay to the company's plant, which is where the name Cementco comes from. When her working life ended in the mid-1980s she was to be scuttled as an artificial reef, but she sprang a leak before she was positioned and sank early, finishing upside down about 400 m north-east of Flinders Reef. She now rests inverted on sand at around 30 m, with the hull bottom at about 16-18 m.

Most of the wreck is easily accessible from outside, and the gaps between the upturned deck and the seabed let divers look into the structure, where machinery hangs from what was the deck. Divers with wreck training can penetrate sections whose floors, in the words of one charter operator, are carpeted with crayfish. The hull is well grown over with corals and sponges and holds large schools of fish, with Queensland groupers, rays and schooling baitfish common.

Because of its depth, bottom time is limited on air, and nitrox extends the dive usefully. It suits advanced divers and is usually combined with a shallower Flinders Reef dive.

Boat access only. Brisbane charters leave from Manly Boat Harbour (Brisbane Scuba departs from the corner of Royal Esplanade and Davenport Drive, Manly) or from Scarborough Boat Harbour on the Redcliffe Peninsula, crossing Moreton Bay and running out through the North West Channel past Bulwer and Comboyuro Point to the northern tip of Moreton Island. Allow roughly 75-90 minutes from Manly in good conditions.

Sunshine Coast operators run south from The Wharf, Mooloolaba, in about 45 minutes. Private boats typically launch at Scarborough or Bribie Island; the open-water crossing around Cape Moreton is exposed and should only be attempted in settled weather with local knowledge. The wreck lies about 400 m north-east of the reef and is usually combined with a Flinders Reef dive.

Exposed open-ocean site north of Cape Moreton. Swell over about 1.5-2 m from the east or north-east and winds over 15 knots from the north or south-east make the site uncomfortable and the crossing rough. Currents are variable and can run across the wreck; operators prefer the slack or a light current, and the dive is sometimes run as a drift if the current is up.

Visibility averages 15 m in summer and 20-30 m in winter. Best on winter mornings after a spell of westerlies.

Descend the line to the upturned hull at about 16-18 m, swim along the keel to get oriented, then drop down the sides to the sand at 25-30 m to look under the hull edges and at the machinery. Trained wreck divers can enter the open sections. Watch no-decompression limits closely, ascend to the top of the hull before returning to the line and do a safety stop.

Nitrox (EAN28-32) extends bottom time. Penetration requires wreck training, lines and lights; the inverted orientation is disorienting.

Brisbane Scuba (Manly) – regular Flinders/Cementco day trips; Go Dive Brisbane and Brisbane Dive Academy – scheduled Moreton trips; Brisbane Sub-Aqua Club runs club trips; Mooloolaba operators occasionally.