Meet the site
South Channel Fort is one of the strangest and most enjoyable dives in Port Phillip: a 0.7 ha artificial island built in the 1880s from granite boulders and concrete on a shoal in the South Channel, part of the defences that guarded the entrance to Melbourne with disappearing guns and a controlled electric minefield. Above water it is a labyrinth of tunnels, magazines and gun emplacements managed by Parks Victoria; below, the tumbled granite blocks that armour its slopes have become a reef of caves, hideaways, caverns and tunnels descending to about 12 m, with seagrass and sand beyond and a jetty on the western side that reaches the bottom at 12 m. The boulders are covered in kelp and colourful sponges, and the gaps between them shelter an unusually rich cast for the bay: giant Australian cuttlefish, southern keeled and Maori octopus, decorator crabs, bluespotted goatfish, southern blue devils in the darker holes – rare this far inside the Heads – and smooth stingrays on the sand. Australian fur seals haul out on the fort's rocks and often join divers, and little penguins nest on the island. The dive can be run as a circumnavigation at about 5 m, as a deeper exploration of the jetty and boulder slope, or as a snorkel on the lee side. The complications are tide and traffic: the South Channel is the main shipping lane into Melbourne, its currents run hard on the flood and ebb, and the fort's position guarantees a sheltered side but also a swept one, so the dive is planned around slack water and the lee. Landing on the island is restricted and visitors stay in the water. South Channel Fort suits Open Water divers and above on a charter or a competent private boat, photographers wanting seals, cuttlefish and granite caves, and snorkellers on a calm day.
What you might see
Australian fur seal, giant Australian cuttlefish, southern blue devil, southern keeled octopus, Maori octopus, smooth stingray, decorator crab, bluespotted goatfish, kelp, colourful sponges, little penguin (on island), leatherjackets, old wife, magpie perch
Location
Victoria's only artificial island, an 1880s granite-and-concrete fort in the South Channel of Port Phillip about 3.5 km north of Sorrento and 6 km north-west of Rye, with rocky slopes to 12 m and a jetty on its western side.
Facilities nearby
Boat departure from Rye, Sorrento, Portsea or Queenscliff (toilets, cafés, air fills at The Scuba Doctor, Bayplay or Dive Victoria); nothing on the island.
Before you make plans
Conditions, access and operator schedules can change. This is a location guide, not a dive plan. Ask a local operator about current conditions and suitability for your training and experience.
Sources & further reading
scubadoctor.com.auen.wikipedia.orgRecord updated 26 Sept 2026. Source claims are being reviewed.