Meet the site
Northern Outer Reef is one of the Dive Shack's listed Adelaide metropolitan boat sites, and it is one of the least documented. It is described as a section of ancient shoreline about 100 m long, running north to south, in 18 m of water. Like Mac's Ground, Milkies and Seacliff, it is a remnant of the coastline that existed when sea level was much lower, now forming a low ledge on the sandy floor of Gulf St Vincent. The Dive Shack highlights vast amounts of sea sponges on the reef, which is typical of Adelaide's deeper offshore ledges where there is less light for algae and more room for filter feeders. Young blue devils are noted in the holes, and the reef has overhangs along its length. Beyond that, expect the usual offshore Adelaide reef fish – old wives, bullseyes, leatherjackets, magpie perch and wrasse – plus invertebrates such as nudibranchs and spider crabs on the sponge-covered rock. At 18 m, the site suits Open Water divers with some offshore experience and Advanced divers. It is compact enough to see in a single dive, and the north-south orientation makes navigation straightforward once the reef is found. The main challenge is locating it: no public position is published, so arrange a mark with the Dive Shack or a club before heading out. Divers who visit are encouraged to share observations with the Scuba Divers Federation of SA so the record can be improved.
What you might see
Sea sponges (abundant), juvenile blue devilfish, old wives, bullseyes, leatherjackets, magpie perch, wrasse, nudibranchs
Location
Section of ancient-shoreline reef about 100 m long running north-south in 18 m off the Adelaide metropolitan coast (exact position unpublished).
Facilities nearby
West Beach or Glenelg boat ramps.
Before you make plans
Conditions, access and operator schedules can change. This is a location guide, not a dive plan. Ask a local operator about current conditions and suitability for your training and experience.
Sources & further reading
thediveshack.com.auRecord updated 26 Sept 2026. Source claims are being reviewed.