Boarfish Reef is the largest and most varied reef in Lonsdale Bight, the sheltered bay inside the Heads between Point Lonsdale and Queenscliff. The Scuba Doctor listing describes it as 'multiple dive sites in one location', extending east–west from the Lonsdale Wall system, with prolific fish life, swim-throughs, caves and rocky outcrops, and it is named for the long-snouted boarfish that are abundant here. Depth is 10–25 m and the rating is Open Water and beyond.

Two features anchor the dive. In 10 m stands a 4 m admiralty anchor, upright and heavily encrusted, a relic of the sailing-ship era when vessels anchored in the bight waiting for pilots or a fair tide; it is the usual start point. Along the northern tip of the reef runs a sponge garden about 400 m long, the densest of the Lonsdale Bight gardens, where the bottom is a continuous carpet of orange, yellow and purple sponges, ascidians and bryozoans. Between the two the reef is broken into outcrops with caves and short swim-throughs, and the fish list is long: southern blue devils, magpie perch, leatherjackets and the boarfish themselves, with southern rock lobster in the caves, nudibranchs and mosaic sea stars on the sponges, yellow sea spiders, and Port Jackson sharks and varied carpetsharks resting under ledges.

Boarfish Reef is the workhorse of the Queenscliff charter fleet: it is inside the Heads, sheltered from most swell, shallow enough for Open Water divers, and big enough to give a different dive on every visit. It is dived on both slacks; the neighbouring Boarfish Reef Drift and Kelp Beds Reef Drift use the same ground as flood-tide drifts when the slack has passed. For macro photographers it is one of the best sites in Victoria, and for anyone new to the Heads it is the natural first dive.

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 10 minutes to the site.

The site is in Lonsdale Bight inside the Heads, 10 minutes from Queenscliff Harbour and 15 from Portsea; the listing carries several alternative Geoff Rodda marks along 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, 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.

Shot onto the reef at 10–12 m at slack. Find the 4 m admiralty anchor standing upright in 10 m, then work the outcrops, caves and swim-throughs at 12–18 m toward the northern tip where the 400 m sponge garden begins; drop to 20–25 m at the outer edge if desired. Navigate back over the reef top, safety stop on the reef, DSMB for pick-up.

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.