Leatherjacket Alley is a shallow natural reef 2 km north-west of Glenelg, made up of naturally formed gutters in the seabed and scattered rock piles at about 10 m. It is named for the variety of leatherjackets found there, including the small pygmy leatherjacket, and it is one of the easiest offshore dives from the Glenelg area because of its modest depth and short boat run. The gutters give the site more structure than most metro reefs.

Their walls carry sponges, sea tulips and algae, and the fish use the channels as corridors. Local guides describe hand-feedable fish and great schools of sea pike that can form what one guide calls a seemingly impenetrable wall. Leatherjackets of several species pick over the rock, and blue devils, wrasse and old wives are common.

Spider crabs and nudibranchs are found in the crevices. At 10 m, bottom time is limited more by air and cold than by depth, which makes Leatherjacket Alley a good second dive after the Dredge, a relaxed site for newer divers, and a place for photographers to spend an hour on macro subjects. It is also close enough to Glenelg to be dived on half-day windows when the sea breeze is expected early.

Visibility is the main variable. Being closer to shore than the wrecks, the site is more affected by stirred-up sand after westerly winds and by runoff after heavy rain. On a clear, calm morning after easterlies, though, the combination of shallow light, colourful sponges and dense fish makes it one of the most pleasant dives off the city.

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 5-10 minutes north-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 sand beside the gutters, follow one gutter along its length at 9-10 m, cross to the next and return. At 10 m there is time for a long, slow dive looking for pygmy leatherjackets and the sea pike schools.

No regular charter; club and private boats from West Beach or Glenelg; occasionally used as a shallow second dive by Adelaide boat groups.