The Not So Deep Wall is McFadyen's name for the sand-edge reef that lies between the classic Bare Island Right route and the Deep Wall proper – a line of large boulders and overhangs at 14–16 m running north-west to Sea Horse Corner, deep enough to be clearer and quieter than the training zones but not as committing as the 15–19 m Deep Wall. Three entries lead to it: the island's western point on very calm days, the natural Pool between the rock formations, and the ordinary boat-ramp start using a gully known as The Shortcut. Whichever you use, the routes converge on the sand edge at about 14 m where the boulders begin.

The wall itself is a mix of big rocks, undercuts and kelp beds with sponges on the vertical faces, and the interest is the same as on the neighbouring reefs: Sydney pygmy pipehorses on the algae, big-belly seahorses on the sponges, cuttlefish in the gaps, and the usual Bare Island fish along the edge. Its real purpose is as a stepping stone. McFadyen explicitly advises completing the Bare Island Right and 15 Metre Reef dives first unless accompanied by someone who knows the site, because the reefs here run in all directions and it is easy to get lost, and because currents in the 14–16 m zone – notably around Sea Horse Corner – often flow against expectation.

Minimum dive time is around 50 minutes and experienced divers stretch it to 90, so a large tank is essential. The safety rule that governs all the outer Bare Island routes applies with force here: if lost, never ascend; head north-east until you reach the island or the mainland and surface only in water shallower than three metres. Done with a knowledgeable buddy it is a fine long dive on the quieter side of Sydney's busiest site.

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.

Choose one of three entries: the western point for experienced divers on flat days, the Pool between the rock formations, or the standard Bare Island Right start at the boat ramp using 'The Shortcut' gully. All routes converge on a sand-edge reef at about 14 m. Navigate north-west along the wall to Sea Horse Corner, then north-east and east along the reef edge back to the exit at the ramp.

Large tank; 50 minutes minimum.

Diveable in virtually all seas, even from the south-east, except the very largest; but McFadyen asks for extremely calm seas for the western point entry and good navigation for the rest. Currents in the 14–16 m range and around Sea Horse Corner can run opposite to expectation, especially on the ebb after a big high tide; dive on a high or incoming tide. Visibility about 10 m average, 15–20 m on the deeper reef in good periods, 1–2 m after heavy rain.

Boats – surface only under 3 m.

Descend at the chosen entry to the 3 m sand, follow the route out to the sand-edge reef at 14 m, and work north-west along the wall of large boulders and overhangs, checking sponges for pygmy pipehorses and seahorses, to Sea Horse Corner. Turn north-east then east along the main reef edge and return to the boat ramp; 50 minutes minimum, 90 for experienced divers. If lost, do not ascend – head north-east and you will hit the island or mainland.

Guided occasionally by Abyss and Sydney Dive Academy; experienced independent divers.