The Mall is the central stretch of Lonsdale Wall, the part of the cliff directly between the traditional 'Lonsdale Wall' mark and Party Point, and it is where many charters drop divers when they simply say they are 'doing the wall'. The Scuba Doctor listing rates it 15–45 m and describes an almost vertical drop with overhangs, ledges and undercuts – the classic stepped profile of the Heads, with a reef flat at about 15 m, a big ledge in the mid-twenties and further terraces to 45 m at the sand.

The name is apt: this is the busy shopping strip of the wall, where the fish density is highest. The listing's species roll is the fullest of any section – southern blue devils in the undercuts, leatherjackets, dusky morwong, southern hulafish in clouds off the face, old wives in schools, southern rock lobster in every crack and giant cuttlefish in season – with occasional Port Jackson sharks and gulf wobbegongs on the terraces and sharpnose sevengill sharks cruising off the wall in deeper water. The guide also records at least four different nudibranch and sea star species, and the encrusting cover of zoanthids, sponges and jewel anemones is as dense as anywhere on the Heads.

For a diver choosing between the named sections, The Mall offers the most complete Lonsdale Wall experience in the recreational depth band: the lip is shallow enough to reach on a short shot line, the 25–30 m ledge is long enough to fill a slack-water dive, and the fish life is reliable. Because the wall continues past 40 m it demands the same depth discipline as the rest of the system, and because the current returns as quickly here as anywhere at the Heads the dive is over when the slack is – typically 20–30 minutes. It is dived on both the flood and the ebb slack.

Boat access only. Charter boats leave from Portsea Pier (Dive Victoria Group, Bayplay) and Queenscliff Harbour (Dive Victoria Group, Red Boats); run time is about 15 minutes. Private boats launch at Sorrento Boat Ramp (Point Nepean Road, Sorrento, all-tide concrete ramp with trailer parking) or Queenscliff Boat Harbour ramp (Larkin Parade, Queenscliff), roughly 15 minutes to the site.

The site is in the middle of the Lonsdale Wall system between the main wall mark and Party Point. Skippers must call Lonsdale VTS (Point Lonsdale) or listen to VHF 12 for shipping movements before dropping divers, and must carry a dive flag; anchoring is not permitted in the shipping channel, so a live boat and a drop-shot or drift float is the normal method.

It is dived only on slack water, either at the end of the flood (SWF) or the end of the ebb (SWE); most operators prefer the flood slack so that any residual current sets into the bay rather than out to sea. Slack water at Port Phillip Heads does not coincide with high or low water: it falls roughly three hours after high or low water at Point Lonsdale, and the usable window is typically 20–40 minutes. Use the Ports Victoria / Port of Melbourne slack-water predictions for The Heads (also republished by charter operators and WillyWeather 'Rip Bank') rather than a standard tide table.

Being outside or right at the entrance, it is exposed to Bass Strait swell: anything over about 1.5 m from the south-west or south, or a strong southerly/westerly wind against the ebb, produces standing waves in The Rip and charters cancel. Northerlies flatten the entrance and give the best days. Visibility is best in late summer and autumn (Feb–May) when the water is clear and the westerlies have eased; winter brings 11–13 °C water and bigger swells but often the clearest days after a run of settled weather.

Heavy rain has little effect this close to the ocean.

Shot onto the lip at 15–18 m. Descend the near-vertical face to a planned maximum of 30 m (Advanced) and swim south along the first ledge with its long undercut, then step up to the 22 m terrace for the return leg. Ascend the face, DSMB from the reef top and drift the safety stop toward the bay.

Sand at 45 m; nitrox for the 25–30 m ledge, trimix optional for the base.

Dive Victoria Group (Portsea and Queenscliff) – double boat dives to the Heads walls most days of the week, site chosen on the morning by slack-water time and swell; Bayplay Adventure Tours (Portsea) – weekend and holiday charters; Red Boats (Queenscliff) – weekend Heads charters; Melbourne clubs (VSAG, Power House Underwater Club, Scuba Diving Melbourne) run their own boats here regularly.