Sweep Reef is the centrepiece of a kilometre-long reef system along the ocean side of Point Nepean, running from Beacon Rock at the western end to Petriana Reef, where the tanker Petriana was lost in 1903. The Scuba Doctor listing, drawing on the Parks Victoria divers' guide, describes it as 'the most prominent feature, positioned midway between the other two reefs', in 3–9 m, and rates it Advanced Open Water for the exposure rather than the depth.

This is Bass Strait reef, not Heads wall: a platform of limestone ledges and gutters facing the open ocean, scoured by swell rather than tide, with kelp on the tops and the encrusting life confined to the undersides of the ledges. The name is the description of the fish life – silver sweep in dense schools over the reef – and with them the open-coast community of the Nepean back beaches: big bluethroat wrasse, zebrafish, magpie morwong, scalyfin, crayfish and abalone in the gutters, weedy seadragons on the sand fringes, and seals and the occasional sevengill shark along the drop to sand. Water clarity here is usually excellent because it is oceanic and unaffected by the bay.

The listing does not encourage the casual visitor: it is 'an advanced boat dive best attempted on ebb tide when swells diminish' and 'divers with any doubts should avoid this site due to the large swells that can occur here'. In practice that means a flat day with a northerly, an ebb tide, a skipper prepared to run out through the Heads and along the back of the point, and divers comfortable in surge. It is dived rarely and almost entirely by private and club boats, and it suits experienced divers looking for undived Bass Strait reef within sight of Portsea. The whole point and its waters are within the marine national park.

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 20 minutes to the site.

The site is on the ocean side of Point Nepean, reached by running out through the Heads and turning east along the back of the point (15–20 minutes from Portsea or Sorrento); there is no shore access because the point is national park. 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 on the ebb slack or a gentle ebb only, when the outgoing tide leaves this side of the reef in relatively still water. 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: 'an advanced boat dive best attempted on ebb tide when swells diminish', and 'divers with any doubts should avoid this site' because of 'the large swells that can occur here'. It faces Bass Strait directly and needs a flat day.

Live drop up-swell of the reef on the ebb. Descend onto the top at 3–5 m and work along the seaward gutters at 6–9 m with the reef as shelter from surge, then back along the inshore side; keep the dive short and ascend under a DSMB for pick-up in the lee.

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.