Port Phillip · Australia · Pinnacle
Castle Rock
A 200 m rock circled in one dive, 18 m sand to 12 m top
Area photo: Kgbo · CC BY-SA 4.0
Castle Rock is a single rock formation outside Port Phillip Heads, sitting on sand in about eighteen metres and rising to around twelve. It is roughly two hundred metres in circumference, with overhangs, walls and swim-throughs around its sides, and a dive can circle it several times without covering the same ground twice.
Where it is and how deep
38.2978° S, 144.5986° EPublished position for this site.
The dive
The shape of the dive is decided by the site. The rock stands alone on sand at about eighteen metres and rises to roughly twelve, so you drop onto the top or onto the sand line and then simply follow it around. At around two hundred metres in circumference, one lap does not take a full tank, and most divers end up circling it several times at different depths.
Each lap can be run differently. The sides carry overhangs, short walls and swim-throughs, so a circuit tucked in close through the structure is a different dive from one out on the sand looking back at the rock. The fixed depth, the lack of current and the easy navigation are what make this a site for newer Open Water divers: the profile does not change as you go round, and the rock is always the thing to come back to.
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.
Sources
- Castle Rock — Scubago/SSI
More dive sites in Port Phillip
Reef
A 10-22 m reef of overhangs and swim-throughs
Wall
A broken wall from 12 m to 30 m, cut with overhangs
Wall
The shallow 8 m top of the Lonsdale wall system
Reef
A 16 m rock platform dived along its winding edge
Wreck
A WWI submarine at 27 m, silt-free inside on the right day
Wreck
A scuttled 1887 ferry at 33-35 m, bow and stern intact
A 138 m guided missile frigate sunk at 30 m
More than a hundred nudibranch species under one pier
Similar dives elsewhere
A manta cleaning station beside a coral-covered Admiralty anchor
Loose bommie field in 14–19 m that rays and sharks cross
Two towers off the sand at 24 m, tops at 14 and 16 m
Resident leaf scorpionfish on bommies at 18 m