Port Phillip · Australia · Wall · Reef
Portsea Hole
A 75 m vertical wall dropping from 12 m to 32 m
Photo: Christopher Mark · CC BY 4.0
Portsea Hole is a depression in the seafloor of Port Phillip about 500 m from Portsea Pier, where the surrounding seabed at 12 m drops sharply to 32 m. A vertical wall roughly 75 m long forms its northern side, undercut with small overhangs that shelter blue devil fish, over a benthic community of invertebrates, encrusting algae, sponges and soft corals.
Where it is and how deep
38.3108° S, 144.7111° EPublished position for this site.
The dive
The dive begins on the flat seabed around the hole at about 12 m and works out to the edge, where the ground falls away sharply to 32 metres. Most recreational profiles here reach 30 m rather than the bottom. The northern side is the reason to come: a vertical wall approximately 75 metres long, usually run in one direction along the face and returned shallower above it.
The wall carries small overhangs, and those are where the animals sit - blue devil fish shelter in them, and the rock around them holds a rich benthic community of marine invertebrates, encrusting algae, sponges and soft corals. Fish assemblages over the drop are diverse and abundant, so the wall itself is consistently busier than the flat sand above the rim.
The hole is a remnant section of the drowned valley of the Yarra River, cut when sea level was lower and the river ran out through what is now Port Phillip. It sits inside the Port Phillip Heads Marine National Park, managed by Parks Victoria: fishing from the shore or at sea is prohibited anywhere in the park, along with taking anything or carrying a speargun.
Marine life and season
- Reef fish swarms
- Macro critters
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Good | Good | Good | Good | Prime | Prime | Prime | Good | Good | Good | Good | Good |
Season follows Port Phillip: The spider crab aggregation runs May–Jul; winter also brings the clearest water, while summer is warmest but greener.
Know before you go
- The wall runs to 32 m, below the 30 m most recreational profiles here use, so it is easy to slip past plan while following an overhang - set a depth floor before dropping over the edge.
Dive videos
Diving Portsea Hole, Victoria, Australia (1080p HD).mp4 · StarangWonda on YouTube
Diving - Portsea Hole - and a shark! 8 Feb 2025 · Colin Grant on YouTube
Questions divers ask
How deep is Portsea Hole?+
The surrounding seabed sits at about 12 m and the hole descends sharply to 32 m. Parks Victoria describes recreational dives here as reaching depths of up to 30 m.
Can you fish or spearfish at Portsea Hole?+
No. The site lies within Port Phillip Heads Marine National Park, where fishing from the shore or at sea is prohibited, as is taking anything or carrying a speargun.
Sources
- Portsea Hole — Wikipedia
- Diving in Australia — Wikivoyage
- Port Phillip Heads Marine National Park — Parks Victoria
Photo credits
- Bright pink encrusting sponge close up on a rock surface underwater by Christopher Mark, CC BY 4.0, via Wikimedia Commons
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