The Bluff, or Rosetta Head, is the most popular shore dive at Victor Harbor and, according to Diving Adelaide, the easiest place in South Australia to find a leafy seadragon, with ten or more possible on a good day. The headland is a 97 m granite dome at the western end of Encounter Bay, formed when molten Encounter Bay Granite intruded older rocks around 475-500 million years ago, and it was the site of a shore whaling station from 1837 into the 1850s. Underwater, the granite continues as big boulders stacked one on top of another, creating holes, ledges and swim-throughs.

The Federation gives depths from 4 m to 40 m, although most dives stay in 5-18 m along the boulders and weed. Sponges and soft corals grow in the shaded gaps, and kelp and other weeds cover the tops. The leafy seadragon population is described as exceptionally healthy, with many juveniles, and a small colony of weedy seadragons lives further out where the current increases.

Other life includes seahorses, crayfish in the crevices, nudibranchs, cuttlefish, sea stars, morwong, blue devils, boxfish, globefish and sweep, and sea lions and seals regularly visit. The Marine Life Network notes that the deeper boulders around the Bluff offer the best diving. Conditions are everything here.

The site is fully exposed to southerly winds and swell, and there are usually particles in the water even on good days. After several days of northerly winds, though, it can be superb. The Bluff suits Open Water divers comfortable with a shore entry and some current, and is a must for seadragon photographers.

Keep your distance from the dragons and avoid disturbing the weed they shelter in.

Victor Harbor is about 1 hour 15 minutes (80 km) south of Adelaide via the Victor Harbor Road. From town, follow the Esplanade and Franklin Parade west through Encounter Bay to the Bluff (Rosetta Head). Park at the small beach in the bend (stairs lead down to the sand) or near the small fishing jetty on the eastern side of the headland.

The safest entry is from the beach, swimming to the jetty; fit divers can use the jetty ladder. Climbing over the slippery rocks by the jetty is not recommended; the rocks behind the jetty can be used on calm days only.

Encounter Bay faces south into the Southern Ocean swell that wraps around Kangaroo Island and Cape Jervis, so Victor Harbor sites are the reverse of the gulf coast: they need northerly (offshore) winds. The best days follow several days of northerlies with low southerly swell, when visibility improves and the swell is blown back; any southerly or south-westerly swell over about 1 m, or strong southerly winds, makes most sites undiveable and stirs up particles. Summer and autumn bring the most northerly days, but good windows also occur in winter ahead of cold fronts.

Tidal currents strengthen around the headlands and islands during large tidal movements. Southern right whales visit Encounter Bay from about June to October – keep legal approach distances. Water is a little cooler than in the gulf.

The Bluff is fully exposed to southerly winds; local guides say 'once you feel the current pick up, it's time to turn around'.

Enter from the beach, swim to the jetty and descend. Head out with the rocky reef and weed on your right shoulder, following the boulders around the headland at 5-12 m and searching the weed for leafy seadragons. When the current picks up, turn and return with the reef on your left shoulder to the jetty.

Diving Adelaide (Glandore) – regular guided leafy seadragon dives at the Bluff when conditions allow; Adelaide Scuba and Underwater Sports – occasional trips; popular with independent divers on northerly days.