Port Phillip · Australia · Reef
The Plateau
A 16 m rock platform dived along its winding edge
Area photo: Kgbo · CC BY-SA 4.0
The Plateau is a broad rocky platform inside the Port Phillip Heads Marine National Park, sitting at around 16 metres. The dive works the rim rather than the middle, winding along the edge of the platform where the rock breaks away. It is old river ground: the platform was part of the bed of the Yarra before the sea came in over it.
Where it is and how deep
38.2958° S, 144.6371° EPublished position for this site.
The dive
You drop onto the top of the platform at around 16 metres and then leave the flat behind. The interest is at the edge, where the rock ends and the ground falls away, and the dive follows that line as it winds around the platform. The edge does not run straight, so the route is a series of curves and corners rather than a heading you hold for the whole dive.
This is the deepest water in Victoria and the bottom beyond the platform lies between 40 and 100 metres, so the edge is a boundary to work along rather than a slope to follow down. The slack period here is short and hard to pick and the currents are a little unpredictable, so the dive is timed tightly and the flat top is the reference to come back onto at the end. The whole site is inside the Port Phillip Heads Marine National Park.
Background
The platform was originally part of the bed of the Yarra: when sea levels were lower the river ran out through the entrance to the bay, and the rock the dive follows is what is left of that course. The water beyond it is the deepest in Victoria, dropping to between 40 and 100 metres. The site now lies in the middle of the Port Phillip Heads Marine National Park, which protects the ground at the entrance to the bay.
Marine life and season
The sources we used don't single out particular species here.
| 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 slack window is short and hard to pick and the currents are unpredictable, so the dive is timed tightly and called off if the flow has not stopped.
- Beyond the platform edge the bottom drops to between 40 and 100 metres, so the rim is followed rather than crossed once you leave the flat top.
Sources
- The Plateau — Scubago/SSI
In The Logbook
- Tides and slack water: the ocean's timetableOcean science · 7 min read
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