The Aspendale reef is one of several concrete-module artificial reefs installed by Fisheries Victoria (now the Victorian Fisheries Authority) in Port Phillip from 2009 onward to improve recreational fishing and to test how quickly engineered habitat is colonised on the bay's featureless sand plains. It lies in 10-11 m of water about 2 km off Aspendale beach and consists of clusters of purpose-cast concrete reef balls and modules laid out within a rectangle marked by four pallet-ball buoys. The modules are a metre or two high with holes and internal voids, and within a few years they were covered in sponges, ascidians, hydroids and red and brown algae and had become home to snapper, leatherjackets, wrasse, old wives, boarfish, red mullet, bearded rock cod, ling and long-finned pike, with schools of small baitfish overhead, octopus in the cavities and rays on the sand between.

It is not a scenic dive in the conventional sense; the interest is in seeing how much life a small amount of hard structure attracts in the middle of nowhere, and in the concentration of fish that results. For divers it is a small-boat site rarely visited by anyone but clubs and photographers, and it is more heavily used by anglers, which means fishing line on the modules and a need to fly a flag and keep an eye on boats overhead. The flat 11 m profile makes it a comfortable long dive for open-water divers and a good first boat dive.

Tyre Reef, an older 1970s artificial reef, lies 1.7 km south and can be done as a second dive; the similar Tedesco Reef is off Seaford further south.

Launch at the Mordialloc Creek public ramp (Beach Road, Mordialloc) or the Patterson River ramp at Carrum and run 3-5 km to the marker buoys, 10-15 minutes in a small boat. The reef is enclosed by four yellow pallet-ball markers at its north, east, south and west corners (approximately 38 02.15 S to 38 02.18 S, 145 04.60 E to 145 04.64 E); anchor on sand outside the markers or tie to a marker if permitted and descend beside a module. It is 2 km from the beach and not a shore dive.

Open bay with no shelter: dive only in light winds, ideally northerly to easterly; any fresh southerly, south-westerly or westerly raises short steep chop on this side of the bay and makes anchoring and re-boarding unpleasant. Visibility is best on the flood tide and in the cooler months and drops after rain because of the Mordialloc and Patterson River outflows. No swell.

Watch for afternoon sea breezes in summer and for anglers, who use the reef heavily.

Descend the anchor or marker line to the sand at 10-11 m, locate the nearest concrete module and work module to module in a loop around the reef, keeping a compass bearing back to the line, then return up the line with a 3-minute stop at 5 m as a courtesy to boat traffic.

No regular operator – private boats and club RIBs; primarily a recreational fishing reef.