The Eliza Ramsden is the best-preserved sailing-ship wreck inside Port Phillip and a textbook of what Corsair Rock did to shipping. She was a three-masted iron barque of 415 tons, 46 m long, built in Glasgow by Barclay Curle in 1874 for the Melbourne businessman Samuel Ramsden, who named her after his wife; she cost £10,000 and had made one voyage. On 24 July 1875 she left Hobsons Bay at one in the afternoon with a light fair wind, and that night ran onto Corsair Rock at the Heads. She was floated off but had taken in too much water, and on Sunday 25 July 1875 she sank where she now lies, upright on the edge of the South Channel.

The Scuba Doctor listing describes her as 'upright and quite badly broken up' but with much still readable: the hull plating and starboard decking are intact, the port-side decking has collapsed – probably from the explosives used in the 1960s to reduce her as a hazard – and the hold is full of the bluestone blocks she carried as ballast. The donkey boiler stands in the wreck. Deck stanchions and small fittings survive in the bow, where the clipper stem was virtually intact until it collapsed in the 2010s. From the stern a natural ledge, Ramsden Reef, runs north-east for about 75 m. Depth is 14 m on the highest iron and 22 m on the sand.

The iron is heavily grown with soft corals and the bright yellow zoanthids of the Heads, and the wreck concentrates fish in the way a reef on a sand plain does: southern blue devils under the plating, old wives, boarfish and wrasse over the hull, bullseyes inside, and giant cuttlefish in winter. Nudibranchs are abundant on the growth. She is a shipping-lane site dived at slack water with a shot and a shipping check, but at 14–22 m she is within Advanced limits and the structure is open, with no penetration, which makes her the standard wreck dive of the Queenscliff fleet and a wreck-specialty training site. She is a protected historic shipwreck under the Heritage Act; nothing may be removed.

Boat access only: 10 minutes from Queenscliff Harbour (Red Boats, Dive Victoria Group) or 12–15 minutes from Portsea Pier across the channel; private boats from the Queenscliff or Sorrento ramps. The wreck lies on the southern edge of the South Channel shipping lane, and the listing requires 'a shipping check with the Point Lonsdale Lighthouse first' – call Lonsdale VTS or monitor VHF 12 – and no anchoring in the channel; a shot is dropped on the wreck at slack. GPS is verified from the 'Shipwrecks Around Port Phillip Heads' book.

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.

Inside the Heads it is sheltered from most swell, but a south-west swell over about 2 m still surges across the top of the wall and a westerly or south-westerly wind over 15–20 knots makes the boat work unpleasant; big seas outside drop visibility to a few metres for a day or two. 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.

Inside the bay and sheltered from all but strong northerlies; visibility 5–15 m, best on the flood slack when clean ocean water has just come in.

Descend the shot onto the hull at 16–18 m. Start at the bow with its collapsed clipper stem and stanchions, work aft along the intact starboard side over the bluestone ballast to the donkey boiler, round the stern and return up the port side; if slack allows, follow Ramsden Reef north-east from the stern for 50 m and back. Ascend the shot or under a DSMB.

Dive Victoria Group (Queenscliff/Portsea) – regular, often the second dive after a wall; Red Boats (Queenscliff) – regular; Bayplay – occasional; a standard wreck-specialty training site.