Port Noarlunga Reef is split by the Gap into northern and southern sections, and while most divers enter from the jetty and explore the northern section and the underwater trail, the southern section offers a quieter alternative. The Dive Shack describes a beach entry involving a snorkel of about 100 m to the southern section, and the Sea Wolves note that the reef's northern and southern sections run parallel to the shore, with about 5 m inside, 8 m outside and a variable gap. The southern reef has the same structure as the rest of Port Noarlunga: a long, flat-topped limestone ridge exposed at low tide, with blocky boulders, ledges and overhangs on the sheltered inside, sparse kelp and weeds, crustose coralline algae and sponges.

Fish life includes old wives, sweep, moonlighters, zebrafish, magpie perch and wrasse, with blue devils, cuttlefish and Port Jackson sharks in season, and a wide range of nudibranchs for macro enthusiasts. Because it avoids the jetty crowds and fishing lines, the southern reef suits divers and snorkellers wanting a calmer experience, and it is a good choice for families snorkelling from the beach. The trade-offs are the surface swim, a beach entry that can be surfy, and proximity to the Onkaparinga River mouth, which reduces visibility after rain.

The whole reef lies within the Port Noarlunga Reef Sanctuary Zone, so no fishing or collecting is permitted. Use a surface marker, as kayaks and small boats use the lagoon, and keep away from the Gap when the tide is running.

Drive to Port Noarlunga (35-40 minutes south of Adelaide) and park on the Esplanade south of the jetty. Enter from the beach south of the jetty and snorkel about 100 m out to the southern section of the reef, as described by the Dive Shack. Alternatively, reach it from the jetty stairs by swimming south through the lagoon past the Gap, or by boat from O'Sullivan Beach ramp (about 10 minutes).

As for the rest of Port Noarlunga Reef: the inside is sheltered from westerly swell by the reef, but the beach entry is surfy in westerlies and south-westerlies. Best after easterlies, at high slack water, on neap tides. The southern section is closer to the Onkaparinga River mouth, so visibility suffers more after rain when the river flows, and tidal currents can run near the Gap and the river mouth.

Snorkel out from the beach to the southern reef, descend on the inside at 4-5 m and follow the reef north or south with it on one shoulder; turn at half gas and return to the beach entry.

Used by the same Adelaide shops and clubs that dive Port Noarlunga (Diving Adelaide, Adelaide Scuba, Underwater Sports, The Dive Shack), though less often than the jetty end.