Inner Corsair Wall is the section of the Nepean-side cliff that lies between Nepean Wall and Corsair Rock, the notorious pinnacle at the entrance. The Scuba Doctor listing describes it as 'a very spectacular wall dive with lots of ledges, caves and drop-offs', with the top of the wall at 10 m and the base at over 60 m. It is one of the best crayfish walls at the Heads – the guide notes good southern rock lobster taken at 38 m, though the site is now within the marine national park where all take is prohibited.

The shallow top is unusual for the Heads walls. At 10 m the reef is kelp-covered and broken, and it is here that the scattered wreckage of the P&O liner RMS Australia (wrecked on Corsair Rock in 1904) lies in 3–4 m of water on the rock nearby, according to the Corsair Rock listing. From the lip the wall falls away steeply, with the same stepped ledges and cut-back caves as Nepean Wall and the same heavy encrusting cover of soft corals and sponges. Blue devils, boarfish and old wives hold the caves, and seals from Point Nepean are regular visitors.

The site is right at the throat of The Rip and the listing is clear that it 'can only be dived on slack water as it is only just out of the Heads'. It also sits technically within the shipping channel even though ships do not normally pass over it, so the usual shipping check and live-boat protocol apply. The combination of a 10 m top and a 60 m base means a single dive can be pitched at any level, but the currents and position make it a site for experienced Heads divers and for the technical groups who use the base. It is dived less often than Nepean Wall and mostly by club and private boats.

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 12 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 just outside the Heads off Point Nepean between Nepean Wall and Corsair Rock; the listing notes that although shipping does not normally transit this exact spot it is technically in the channel. 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. The listing states it 'can only be dived on slack water as it is only just out of the heads'; charters prefer the flood slack.

Shot onto the 10 m reef top at slack. Drop over the lip and descend the face to the planned depth – 30 m recreational, 38–50 m technical – exploring the ledges and caves, then return to the shallow top and finish the dive on the kelp-covered reef looking for RMS Australia wreckage before ascending under a DSMB.

Base 60 m+; trimix; slack water only; drift deco under DSMB. Rebreather friendly.

Dive Victoria Group (Portsea/Queenscliff) – runs the deep Heads walls for advanced and technical divers on suitable slack-water days; Red Boats (Queenscliff) – deep-wall and technical charters on request; otherwise private club boats (VSAG, Power House Underwater Club, Scuba Diving Melbourne). Not a routine training-boat site.