Portsea Hole

Meet the site

Portsea Hole is the most-dived deep site in Victoria and, for most Melbourne divers, the place where they made their first dive past 20 m. It is a fragment of the drowned river valley that runs out through the Heads: a natural amphitheatre in calcarenite where, in the words of the Scuba Doctor listing, 'a vertical wall approximately 75 metres long' descends from a reef top at 12 m to sand at 27 m, with the floor then falling into a sand bowl that bottoms at 33 m. West of the sandy depression are rocky ledges and outcrops; east and north the edge of the South Channel shipping lane runs past within a few boat-lengths.

The wall is short but it is a real Heads wall, and the tidal flow along the channel has clothed it accordingly. Parks Victoria and the listing record sixteen sponge species, with ascidians, bryozoans, hydroids and zoanthids between them, and the fish assemblage is described as 'diverse and abundant': southern blue devils in the undercuts, barber perch and butterfly perch in clouds along the face, southern hulafish, silver sweep, jackass morwong and bluespotted goatfish on the sand edge. Nudibranchs are plentiful on the sponges and short-headed seahorses and pipefish are found in the hydroids on the sand rim. Giant cuttlefish appear in winter, and the boat-shaped wreck of a 13 m fishing vessel scuttled in the early 1980s lies 36 m away at 25–27 m (listed separately).

The site is on the edge of the shipping lane and the tide runs through it, so it is dived at slack water with a shot and a live boat and a shipping check; but it is inside the bay, five minutes from Portsea Pier, and sheltered from most weather, which is why it is dived so often. It is the standard site for Advanced deep-dive training on the peninsula, a reliable first dive of a double before a Heads wall, and a good site in its own right for anyone who has not seen a Victorian sponge wall.

What you might see

Sixteen-plus sponge species, ascidians, bryozoans, zoanthids, southern blue devil, barber perch, butterfly perch, southern hulafish, silver sweep, jackass morwong, bluespotted goatfish, nudibranchs, short-headed seahorse, pipefish, giant cuttlefish (winter)

Location

About 500 m north-east of Portsea Pier inside Port Phillip, a drowned amphitheatre of the ancient Yarra River valley on the southern edge of the South Channel; the Portsea Hole Wreck lies 36 m to the north-west.