The Bare Island Bombora is a solitary reef rising off the sand about 250 m due south of the island, and it is where the big fish live. Two small shallower sections form its peaks and beneath them are large overhangs, and under those overhangs sit old man snapper of a size McFadyen says you will very rarely see anywhere else, together with huge schools of bream, sweep, luderick and ladder-finned pomfrets and large kingfish patrolling the edge. It is also seadragon country – 25 were counted on one crossing – and the sand edge on the way out is worth watching.

The catch is getting there. The dive starts from the eastern side of the island's rock platform at the back-left corner, swims out and south, then follows the sand edge on a compass course for 10–15 minutes to reach the bommie, and repeats the exercise in reverse. Currents run between the island and the bombora, sometimes against expectation, the sand offers almost no landmarks, and if visibility drops the navigation becomes a guessing game with a long surface swim among fast boats as the penalty.

McFadyen's conditions are strict: completely calm seas, at or near high tide, a very experienced diver who is good on air, and at least a 12 L tank. Met, they buy a dive on an untouched reef that most Bare Island regulars have never seen, with fish life more like an offshore site than a shore dive. It is a good target for divers who have done the Deep Wall and the Isolated Reefs and want the last piece of the Bare Island map.

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.

Go down the stairs and to the back-left corner of the island, entering on the eastern side of the rock platform, not the southern side. Swim out 20 m, then 20 m south, take a compass bearing south-east to the sand edge and follow it south for about 250 m (10–15 minutes) to the bombora. Return north-east to the sand edge and follow it back to the bridge.

At least a 12 L tank; only at or near high tide in completely calm seas.

Only in completely calm seas and at or near high tide. The bombora sits in open water south of the island where swell from the east or south-east breaks over its shallow peaks, and the 250 m crossing is over featureless sand with current running between the island and the bommie, sometimes opposite to expectation. Poor visibility makes the navigation genuinely difficult; there are few distinctive features on the way and a long surface swim among boats if you have to give up.

Winter high tides after westerlies are the best combination.

From the eastern platform swim 20 m out and 20 m south, then bear south-east to the sand edge and follow it south about 250 m to the bombora, watching for seadragons on the way. Circle the bommie's two shallow sections and large overhangs, then return north-east to the sand edge and follow it back north to the bridge; turn at half gas without fail.

Rarely guided; Abyss and Sydney Dive Academy occasionally as an advanced navigation dive. Experienced independents and St George Scuba Club.