Nepean Reef is the rock at the very tip of Point Nepean, the eastern jaw of The Rip, and it carries two twentieth-century wrecks that the Scuba Doctor guide lists together under the reef and separately by name. The Parks Victoria divers' guide places the SS Time 'midway along the northern side', dominated by 'two huge boilers lying in the middle of the shipwreck remains', and the Campbell 'at the extreme western end, under and just to the north of Campbell Rock'.

The Time was a steel cargo steamer of 3,322 tons, 104 m long, built at Sunderland in 1913. Inbound from Sydney under Captain William McClenaghan with 41 crew, she strayed into the red sector of the Lonsdale light and at 3.10 am on 26 August 1949 drifted onto Nepean Reef. The Queenscliff lifeboat took off her whole crew by that evening. She stood on the reef as a landmark for more than ten years before being blasted – partly, the listing notes, for a film – and her wreckage is now scattered over a wide area, the two boilers the only substantial pieces. The Campbell was a 135-ton Norwegian-built steel whale-catcher of 1911; her steering failed on a passage from Sydney to Melbourne and on 13 June 1914 she struck Corsair Rock at 8 knots and was carried onto the reef. All her crew survived in large seas; the only casualty was the captain's terrier.

Both wrecks lie in 1–9 m on a reef that the ebb pours over at several knots and that breaks in any swell. The guide's advice is to dive from a boat at the last of the ebb and early flood so that the pick-up is inside the Heads rather than out to sea, and only in extremely calm conditions. Kelp and coralline algae cover the plates and boilers, crayfish and abalone live in the wreckage, and sweep, wrasse and seals work the reef. It is a site for experienced divers with a knowledgeable skipper, dived rarely and of interest mainly for its history; both are protected historic shipwrecks.

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 12 minutes to the site.

The site is at the very tip of Point Nepean on the Nepean-side entrance reef, 10–12 minutes from Portsea; the boat holds off in deeper water and drops divers on the reef, which breaks in any swell. Scuba Doctor notes the GPS marks 'are known to be wrong' – rely on the boilers, which are visible from the surface in calm water, and on a skipper who knows the reef. 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 at the end of the ebb (SWE); on other tides the current across the site is unworkable. 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's guidance: 'best dived from a boat at slack water', at 'the last of the ebb, early flood', because 'it's much easier to be retrieved inside Port Phillip for your exit strategy rather than out to sea'; the Time page adds it 'must be dived in extremely calm conditions at slack water' as 'the area is prone to unexpected ocean swells'.

Live drop at the end of the ebb onto the Time's boilers at 5–8 m, work the scattered plating and machinery around them, then, if time allows, move west along the reef to Campbell Rock and the whaler's remains in 3–9 m; turn early, and ascend under a DSMB as the flood starts so that the boat picks you up inside the Heads.

No regular scheduled charter – dived from private and club boats (VSAG, Power House Underwater Club, Scuba Diving Melbourne) and occasionally by Dive Victoria Group or Red Boats when a group requests it.