The Glenelg Tyre Reef is part of the same offshore artificial reef complex as the Dredge and Barge, and is one of South Australia's early experiments in building fish habitat. According to the Marine Life Network, the program followed an American scientist's advocacy of artificial reefs around 1970; a first attempt off Henley Beach failed when storms scattered the material, and around 25,000 tyres were then deployed off Glenelg in the early-to-mid 1970s, with the tetrahedral modules seen today set in 1983. The reef is a field of tyre tetrahedrons and bundles spread over sand at about 18 m.

They are low, relatively uniform structures, so the dive is less about scenery and more about what lives in and around them. The tyres are covered in sponges and small invertebrates and act as shelter for King George whiting, bullseyes, strongfish, silver drummer and old wives, while spider crabs, cuttlefish and nudibranchs are regularly found. Divers also report a fair collection of lost anchors, testament to the site's popularity with fishers.

The modules have deteriorated over the decades and some straps have perished, leaving loose tyres and strapping that can snag equipment. Because the modules look much the same, it is easy to lose track of the anchor, so a compass is essential. This is not a destination dive in itself, but it is a useful alternative when the wrecks are busy, a relaxed second dive at a similar depth, and an interesting look at how fish have colonised man-made structures on an otherwise featureless seabed.

It suits divers comfortable with open-water boat diving and navigation in variable visibility. Local shops note that large sharks, including white sharks, have occasionally been reported in the area during spring and summer salmon runs, as they are elsewhere off Adelaide.

Boat access only. Adelaide Scuba runs its charters from its shop on the Patawalonga at Glenelg North, with the boat leaving through the Patawalonga/Holdfast Shores entrance; private boats launch at the West Beach boat ramp (Barcoo Road end of the West Beach dunes, large trailer park, fee payable) or the Glenelg (Holdfast Shores) ramp. From Glenelg it is a run of about 10-20 minutes due west in flat water.

Use GPS marks: the sites are low-relief and cannot be seen from the surface, and there are no public moorings, so anchor in sand off the structure and leave a boat attendant with a dive flag up because charter and fishing traffic is steady on weekends.

The metro coast faces west into Gulf St Vincent, so the rule is simple: offshore easterly winds flatten the sea and clear the water, while westerlies and south-westerlies build a short, steep chop and stir up the silty bottom. In summer the south-westerly sea breeze usually arrives by late morning or early afternoon, so boats aim to be back in by lunchtime. Northerlies are workable when light.

The gulf has a mixed, small-range tide with 'dodge tides' (neap periods when the water barely moves) that give the easiest diving; strong spring tides can run noticeably across the offshore wrecks. Visibility drops for several days after strong westerly blows and after heavy rain when stormwater and Patawalonga/Torrens outflow reach the coast.

Anchor in the sand at the edge of the tyre field. Take a compass bearing, then swim slowly along lines of tetrahedrons at 16-18 m, checking under each for crabs, cuttlefish and wobbegongs. The modules look alike, so turn on a reciprocal bearing at half gas and return to the anchor for the ascent.

Occasionally visited by Adelaide Scuba and club boats (Underwater Sports, The Dive Shack) as an alternative or add-on to the Dredge and Barge; mostly dived from private boats out of West Beach.