The reefs off Cape Dombey, below Robe's white-and-red Obelisk and the modern lighthouse, are the town's main open-coast dive. The Marine Life Network describes a shallow, kelp-covered rocky bottom at 7-12 m, with limestone reef cut by crevices and overhangs, large boulders and caves with interesting marine life. The Obelisk, built in 1855 as a navigation marker, and the 1972 lighthouse are popular lookouts, and from either you can read the swell before committing.

Underwater it is classic Limestone Coast terrain: a canopy of kelp and brown algae over pale limestone that the swell has carved into ledges, undercuts and small caves. The crevices hold southern rock lobster, blue-throat wrasse, magpie morwong, sweep, leatherjackets and old wives, and the sand channels host rays and flathead. Seadragons – both weedy and leafy occur along this coast – may be found in the weed. Cold water and upwelling in summer give the reef a lush, temperate feel similar to western Victoria.

The catch is exposure. Cape Dombey takes the full force of the Southern Ocean and there is no dive shop or charter in Robe, so the site is dived by locals and visitors with boats on genuinely flat days. Robe itself is a historic 1840s port with accommodation, restaurants and a sheltered harbour, making it a pleasant base for a Limestone Coast trip that combines coast and Mount Gambier caves. It suits self-sufficient divers with boat experience in temperate open water. Fills and hire are 130 km away in Mount Gambier, so bring enough cylinders for the trip.

Robe is about 130 km north-west of Mount Gambier and 340 km south-east of Adelaide. Launch from the Robe marina/boat ramp (Lake Butler) and run a few minutes west around the point to the reef off Cape Dombey below the Obelisk and the Robe lighthouse. The Obelisk car park and lighthouse lookout on Cape Dombey Road give a view of conditions before launching.

There is no dive charter in Robe; divers use private boats.

The Limestone Coast faces the full Southern Ocean, and prevailing south-westerly swells of 2-4 m are the norm, especially May-October. Open-coast 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. Cape Dombey is fully exposed to south-westerly swell; the Godfrey Islands and Guichen Bay give lee options on marginal days.

Anchor in a sand patch near the reef edge at 8-10 m, work along the crevices and overhangs under the kelp, check boulders and small caves for lobster and fish, and return to the anchor at half gas.

No regular operator – private boats from Robe marina; visiting Adelaide/Mount Gambier clubs occasionally.