Southend sits at the southern end of Rivoli Bay where the coast turns into Canunda National Park, and the Marine Life Network lists the shallow rocky reef offshore from the northern end of the national park as a dive site – with the warning that it is very exposed. It is little dived and little documented, which is part of its appeal for self-sufficient locals.

The reef is typical of the region: limestone and calcarenite ledges carpeted in brown algae and kelp, with gutters, sand channels and overhangs sheltering rock lobster, wrasse, leatherjackets, sweep and occasional seadragons. Southend is a lobster-fishing village, and the waters south towards Canunda and Lake Bonney are some of the most productive rock lobster grounds in the state. The Canunda coast adjoins a sanctuary zone of the Lower South East Marine Park further south, so check zoning before taking anything.

History is close at hand. The iron barque Geltwood was lost with all 31 people in June 1876 about 16 km south-east of Southend, and her anchor stands as a memorial on Cape Buffon Drive. The wider Southern Ocean Shipwreck Trail covers several other wrecks in this stretch of coast. For divers, Southend is a place to try on a genuinely calm day – when the swell drops, it offers uncrowded shallow reef, easy snorkelling and a quiet town with a caravan park. It suits experienced shore divers and those with small boats who can judge the Southern Ocean, and it pairs well with a visit to the Geltwood memorial.

Southend is about 70 km north-west of Mount Gambier via Millicent (turn west at Millicent towards the coast) or 20 km around Rivoli Bay from Beachport. Park in the town near the foreshore or at Canunda National Park car parks along Cape Buffon Drive, where the Geltwood anchor memorial stands. Enter from the beach or low rock platforms in calm conditions, or launch a small boat from the Southend ramp and run a short distance to the reef.

The Limestone Coast faces the full Southern Ocean, and prevailing south-westerly swells of 2-4 m are the norm, especially May-October. Shore and boat dives need a genuine calm spell: swell under about 1 m, light winds, ideally northerly or north-easterly offshore breezes, and a few settled days for visibility to recover. Summer south-easterly sea breezes build most afternoons, so dive early.

Heavy winter rain brings tannin-stained run-off from drains and creeks that reduces visibility near shore. Autumn (March-May) usually has the most calm days and the best visibility. Southend's reef is described as very exposed; Canunda's coast is known for big surf.

From a sheltered entry, fin out to the reef in 3-6 m and explore gutters parallel to shore, keeping track of surge and exit points; turn at half gas.

No regular operator – private boat or independent shore diving.