Mimosa Rocks National Park covers about 17 km of coast between Bermagui and Tathra. It takes its name from the paddle steamer Mimosa, which struck rocks just north of Aragunnu Beach in 1863. The rocks themselves are volcanic sea stacks and platforms, formed from ancient lava and ash layers, rising from the sea off the beach. The Sapphire Coast guide calls Aragunnu an ideal location for snorkellers and divers, while warning of strong rips and sharp rocks.

Underwater, the rocks and surrounding reefs have kelp and crayweed in the shallows, boulders and gutters deeper, and sand at the base. Typical fish include blue groper, luderick, eastern rock blackfish, sweep, bream, silver trevally, leatherjackets and wrasse, with stingrays and flathead on the sand. The gutters along the rocks are productive for fish (the same gutters are fished from shore for bream, salmon and mulloway). Octopus, sea urchins and nudibranchs are common. Remains of the Mimosa were salvaged and dispersed long ago; no dive account of the wreck was found.

The site suits experienced snorkellers and shore divers on calm days, and it is a good option for campers at Aragunnu. It is exposed, so conditions must be checked carefully. There is no detailed published dive description, so depths here are indicative. The national park setting, campground and quiet beaches make it a pleasant base.

From the Tathra–Bermagui Road, turn off to Aragunnu campground in Mimosa Rocks National Park; the campground is about 3 km down an unsealed 2WD road (park fees apply). Park in the day-use area and walk a short distance to Aragunnu Beach, which sits at the campground entrance. Snorkellers and divers enter from the beach and swim to the rocks.

Boats can reach the rocks from Tathra (Kianinny) or Bermagui ramps in about 20–30 minutes.

The Sapphire Coast guide warns of strong rips and sharp rocks at Aragunnu. The coast is exposed to swell from the north-east through south; only dive with swell under about 1 m, preferably in westerly weather. Morning is usually the calmest time before sea breezes.

Visibility falls after rain from nearby lagoons.

Enter from the sheltered end of Aragunnu Beach, swim to the rocks and follow the reef around their base at 5–12 m, watching for rips. Return to the beach before you tire. By boat, anchor off the sea stacks and circle them.

No regular operator. The Sapphire Coast guide describes Aragunnu as ideal for snorkellers and divers; visited independently by campers and local divers.