The Stanvac Barges are among the oldest artificial reefs in Gulf St Vincent, three barges deliberately sunk in 1954 on a sandy bottom about 5 km west of Port Stanvac. The largest is the Saurian, a coal lighter converted from a dredge, about 50 m (163 ft) long; the other two are smaller barges, each about 20 m by 15 m (71 x 49 ft), lying 33 m apart roughly 100 m north-east of the Saurian and oriented north-east to south-west. After seven decades on the bottom, the barges are heavily colonised and act as a magnet in an otherwise featureless seabed.

The Federation describes prolific fish life, and the Marine Life Network lists old wives, pike, strongfish, gurnard, flathead, bullseyes, cuttlefish, blue devils, morwong, perch and catfish. On calm days hammerhead sharks have been seen at the surface. Visibility is often better than inshore because the site is well offshore.

Depth is the main constraint. With the seabed at 28-30 m, no-decompression time on air is short, and the wrecks are too far apart to link on one dive – the Dive Shack recommends multiple dives to see them all. This makes the site best suited to Deep-certified or experienced Advanced divers using nitrox, who can plan a compact dive on one structure and ascend on a shot line.

The barges are a good choice for experienced local divers wanting something quieter and deeper than the Glenelg wrecks, and for anyone interested in the history of Adelaide's artificial reef experiments, which began here decades before the Dredge and Barge.

Boat access only. The usual launch is the O'Sullivan Beach boat ramp (off Galloway Road, O'Sullivan Beach; multi-lane ramp with breakwater, large trailer park and toilets), about 30 minutes' drive south of the Adelaide CBD. From the ramp run north-west along the coast to the GPS mark.

There are no public moorings: anchor in sand clear of the structure and keep a boat attendant on board with a dive flag, as fishing boats work these sites heavily. Charters from Adelaide Scuba and club boats sometimes use Glenelg or West Beach instead.

Like the rest of the metro coast, these sites face west into Gulf St Vincent and are best in offshore easterly winds, which are most common on summer and autumn mornings and on clear winter days. Westerly and south-westerly winds build chop quickly and make anchoring and recovery uncomfortable; the summer south-westerly sea breeze typically arrives late morning to early afternoon. Tidal streams in the gulf are modest but noticeable offshore on spring tides; neap 'dodge tide' days, when the water barely moves, give the easiest diving.

Visibility is usually better than at Glenelg because there is less river and stormwater influence, but drops after strong westerlies. Being further offshore, the deeper sites need a genuinely calm forecast.

Plan one barge per dive: drop a shot on the Saurian mark, descend to 28 m, circuit the hull and ascend on the shot. On a second day or second dive, shot the two smaller barges (33 m apart, about 100 m north-east) and swim between them. Watch no-decompression limits.

EANx 28-30 recommended; shot line essential for descent/ascent.

No regular charter; occasional club dives (Sea Wolves, Underwater Sports) and private boats from O'Sullivan Beach.