Barwon Bluff South is the ocean face of the Bluff, where the older sandstone that underlies the basalt cap has been carved by Bass Strait swell into a pincer-shaped reef that juts into the sea at the eastern end of the long sweep of Thirteenth Beach. This is the side that Parks Victoria's description of sandstone arches and colourful sponge gardens refers to, and it is the richer and more dramatic of the two Bluff dives. From the shelf the reef drops through ledges and gutters to 6-9 m along its outer edge, with overhangs and small arches cut into the soft rock and thick forests of giant kelp and crayweed on the tops that sway with every surge.

The intertidal zone is dense with limpets, whelks, barnacles and mussels, and below the kelp the shaded rock carries sponges, sea tulips, feather stars and sea slugs in quantity. The fish are the Victorian open-coast set: Western blue groper cruising the gutters, leatherjackets of several species, magpie perch, boarfish, herring cale and zebrafish in the kelp, Port Jackson sharks tucked under the ledges and smooth stingrays and giant rays on the sand at the base of the reef. Somewhere under the sand 390 m to the south lies the Earl of Charlemont, the immigrant ship wrecked here in 1853; it is buried and rarely visible.

The dive is exposed. Any south-westerly swell breaks across the shelf, surge works through the gutters and the entry becomes dangerous, so this is a site for the flattest days, most reliably in autumn and early winter after a run of northerlies, and for divers comfortable with kelp and surge; The Scuba Doctor's remark that for the experienced the swell adds to the challenge and beauty is an honest description of the trade. On such a day it is one of the best shore dives within an hour and a half of Melbourne.

From Barwon Heads village take Bluff Road up the headland to the first car park (beach marker 28W), which suits dives on the southern side. Gear up, walk down the ramp to the beach (about 150 m) and out onto the rock shelf, and enter from the shelf edge. Swim toward Point Flinders and the kelp beds.

Exit on the shelf at the same point. Look at the sea from the crest before committing; the southern side takes the full Bass Strait swell.

A Bass Strait shore dive: diveable only with little or no swell (under about 1 m at the Bluff) and light winds, ideally northerly to north-easterly; any south-westerly swell or southerly wind breaks over the rock shelf and makes the entry dangerous and the water surgy and murky. Autumn and early winter give the most flat days. Avoid the eastern (river) side after rain, when the Barwon River discharges brown water and visibility collapses; the western side clears sooner.

Check the sea from the lookout on the Bluff before gearing up; if there is white water on the shelf, do not dive. Dive around high tide for depth over the shelf, but be aware that high tides cut off the beach below the cliffs. The southern side is fully exposed to south-westerly swell and needs the flattest conditions of the two; in return it is less affected by river colour and usually has the better visibility.

Enter from the shelf edge on a flat day, descend to 3-4 m and swim seaward and west toward Point Flinders through the kelp, work the sandstone ledges, gutters and small arches at 5-9 m along the outer face of the pincer reef, turn at half gas and return inside the kelp line to the shelf, ascending in its lee.

No regular commercial operator – dived independently and by Geelong and Melbourne clubs; Bay City Scuba (Geelong) and Dive Victoria Group (Queenscliff) are the nearest shops.