Bare Island is Sydney's most-dived site and one of the best temperate shore dives in Australia. The island is a squat sandstone fort built between 1881 and 1889 to James Barnet's design as Botany Bay's sole defence against a feared Russian attack – so badly built that a royal commission followed and Barnet resigned – and it is joined to La Perouse by a timber footbridge. Around it lies a mosaic of sand channels, kelp gutters, sponge-covered boulder reefs and short walls that McFadyen has mapped into a dozen distinct dives: Right (western side), Left (eastern side), 15 Metre Reef, Deep Wall, Not So Deep Wall, Isolated Reefs, Bombora, the Circumnavigation and the Larpa drift, each covered in its own entry.

Bare Island Right is the classic. From the old boat ramp you cross five minutes of sand to a reef edge marked by the Shark Fin rock, follow it west through a kelp gutter and over more sand past the Sea Tulip Rocks to a wall with deep overhangs and The Cave at 14–15 m, its roof hung with gorgonians. What makes the site famous is macro: red Indianfish resident since about 2004, Sydney pygmy pipehorses in brown, red and white, big-belly seahorses on the sponges, miniature painted anglerfish, several pipefish species, nudibranchs by the dozen, and – historically in numbers, scarcer since 2009 – weedy seadragons in the kelp.

Wobbegongs, Port Jackson sharks in August, blue groper, cardinalfish, flathead, stingarees and numbfish round it out, and the sponge, sea-squirt and lace-coral cover is exceptional for water this accessible. Visibility was 4–5 m through the 1990s and improved markedly after 1999 to an average near 10 m, with 15–30 m on good days. Because it is diveable in almost any weather, it is the default when everything else is blown out, which explains the crowds; go early, dive on a high tide, and never surface mid-water because of the boats under the bridge.

Bare Island is part of Kamay Botany Bay National Park, 20 km from the CBD. Drive down Anzac Parade to the La Perouse loop and park on the edge of Anzac Parade as close to the island's access road as possible (arrive before 8 am on weekends). Gear up at the car, walk 200 m down the access road and across the timber footbridge to the island, then down the stairs to the rock platform.

For the Right/Western dive turn right at the bottom of the stairs and walk 50 m along the platform to the old boat ramp; enter in 3 m and swim north-west across the sand about 5 minutes to the main reef marked by the 'Shark Fin' rock and an old outboard motor. Exit at the same ramp. Total carry from car to water is about 300 m, all on formed path and bridge.

Bare Island is the most weatherproof dive in Sydney. The Right (western) side can be dived in virtually all seas, even south-easterlies, because the island and Kurnell peninsula shelter it; only in huge seas – over about 5 m average – is it undiveable, and in moderate seas almost any part of the reef is safe. North-easterly swell over 1.5 m creates surge on the eastern (Left) side.

Tide has little effect on the main dive; the outgoing tide after a big high can generate current in the deeper 14–19 m sections and visibility is usually better on the high. After prolonged heavy rain visibility drops to 1–2 m for several days from stormwater. Weekend crowds and boat traffic under the bridge are the real constraints – dive early.

Enter at the boat ramp, swim north-west over the sand for five minutes to the Shark Fin and outboard motor, follow the reef edge north-west then west through the rocky kelp gutter, across sand at 25 m to the orange sponge rocks and 44-gallon drum, then to the Sea Tulip Rocks at 8.5–9 m (seahorses, Indianfish) and on to the wall with its deep overhangs and The Cave at 14–15 m. Turn at Sea Horse Corner, return along the sand edge and kelp and exit at the ramp – 60 to 80 minutes.

Every Sydney dive school uses Bare Island: Abyss Scuba Diving, Pro Dive Coogee and Cronulla, Sydney Dive Academy, Dive Centre Bondi, Frog Dive and Southern Cross Divers run courses, guided dives and night dives here weekly; dozens of independent divers most weekend mornings.