The San Remo Bridge dive is the most demanding shore dive on Phillip Island and one of the few genuine current dives accessible from land in Victoria. The bridge crosses The Narrows, the 300 m channel through which the whole of Western Port's eastern arm floods and drains, and beneath its pylons the scoured bottom is rock rather than sand: a reef of ledges and low bommies between 3 and 13 m that is, in Scuba Doctor's words, covered in corals and supports lots of marine life. The constant six-knot flow has produced a community more like an offshore pinnacle than a bay reef – dense soft corals and sponges, sea whips, ascidians, hydroids and bryozoans coating every surface, with crayfish in the ledges, big schools of sweep and trevally holding in the eddies behind the pylons, rays on the sand pockets and the seahorses and nudibranchs familiar from the two jetties either side.

It is the intensity of the setting that people remember: bridge traffic thundering overhead, the pylons vibrating, and a wall of moving water visible on the surface. The warning attached to the dive is unusually blunt for a directory page – do not even think about diving this site unless you are an extremely fit diver who is highly competent in very fast currents – and it should be taken literally. The usable slack is about ten minutes.

A diver who mistimes entry or lingers is carried south past San Remo Jetty and out towards the entrance bar and the Cape Woolamai rip, or north into the eastern arm, with no easy exit either way. In practice the dive is done as an extension of San Remo Jetty by divers who have already learned the tides there, treating the bridge reef as a brief bonus at high-water slack rather than a destination in its own right. For those few it is a memorable glimpse of what strong tidal flow does to temperate reef life.

Follow the San Remo Jetty directions: Bass Highway to the San Remo roundabout, then Marine Parade; park by the co-op or on the foreshore. The bridge reef lies 220 m north of the jetty, so most divers enter from the beach beside San Remo Jetty on the last of the flood and let the dying current carry them to the bridge pylons, or they enter at the small beach directly below the San Remo end of the bridge. Have a shore support person and a pre-agreed pick-up on the Newhaven side (Beach Crescent) in case the ebb turns early.

Walk from car to water is under 100 m either way.

Entirely tide-driven. Streams under the bridge reach 6 knots; the only window is the end of the flood, when a fit diver has roughly ten minutes on the reef before the ebb begins and the flow must be used to get back to shore. Use the Newhaven tide tables, choose neap tides, and abort if the water is still visibly running when you planned to enter.

Wind is a secondary issue, although a strong southerly against the ebb throws up standing waves in The Narrows. Visibility falls after heavy rain and in the days after a big swell has stirred the entrance bar. Daylight only, and only after several dives at San Remo Jetty on the same tides.

Enter beside San Remo Jetty 15–20 minutes before predicted high water and drift north on the last of the flood to the bridge, descending onto the reef between the pylons at 8–13 m. Spend the ten or so minutes of true slack on the reef, staying within a pylon span of your exit line. The instant the ebb begins, move to the San Remo shore side and use the reef and pylon bases as handholds to work back south to the jetty beach, or, if already committed, surface under the Newhaven side and exit at Beach Crescent.

SMB, flag and shore cover are mandatory.

No operator runs this dive; it is done by a handful of very experienced local and Melbourne club divers who know San Remo Jetty well. Not offered as a guided dive.