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Diving the Cape Peninsula and False Bay/Castor Rock

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Diving the Cape Peninsula and False Bay : Castor Rock
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Diving the Cape Peninsula and False Bay/Castor Rock

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The dive site Castor Rock is an offshore rocky reef in the Simon's Bay area on the Cape Peninsula side of False Bay, near Cape Town in the Western Cape province of South Africa.


Map of the dive sites near Roman Rock. Castor rock reef is the large reef to the north


  • S34°10.60’ E018°27.56’ (North reef pinnacle)
  • S34°10.68’ E018°27.59’ (Main reef northern pinnacle)
  • S34°10.74’ E018°27.61’ (Main reef central pinnacle)
  • S34°10.81’ E018°27.65’ (South reef pinnacle)

An extensive area of rocky reef north of Roman Rock lighthouse

This site is in a Marine Protected Area (2004). A permit is required. The site is probably entirely inside the Boulders Restricted Zone.


The area is shown on SA Navy charts as "Castor Rock".


Maximum depth is about 18m to the south, and 22m to the north. The highest point on the reef is about 4m deep.


This is an extensive reef of granite. Basically a very large outcrop with occasional high areas, small gullies, ridges, boulders, small crevices and overhangs. The edge of the reef is penetrated at irregular intervals by small sandy bottomed gullies between the ridges,

Castor rock has a very different character to Roman and Rambler rocks. The reef top is of moderate relief, with relatively shallow sandy gullies, small overhangs and boulders, and has some steep areas at the edges. The sand to the south is coarse and shelly in places.

There is a high corestone reef a few metres across the sand to the north of the main reef known as North Pinnacle, which is reported to be a good site with overhangs and swimthroughs.

There is also a reef section to the south known as South Pinnacle, or occasionally as Wonder reef, between Castor Rock and Roman Rock that is similar to the main reef, but possibly higher profile on average. This section of the reef connects to the main reef by a narrow isthmus on the west side.

Geology: Granite corestone outcrops and boulders of the late Pre-Cambrian Peninsula pluton.


The site is exposed to winds from all directions, which can produce an unpleasant choppy sea, and make it difficult for the boat crew to see a diver on the surface. Generally considered a winter dive, as this is when conditions are most likely to be good, but can be dived any time the swell is low and the visibility is acceptable. This can happen any time of the year after a period of light winds when the swell is low or short period.

Get in

Always dived from a boat. The site is 3.3km from Simon’s Town, or 5.6km from Miller’s Point.


Leopard catshark
Scorpion fish
Shoal of Galjoen
Reef scene with green soft corals
Red cucombers and Striped anemones
Shy shark

Marine life

Large variety of invertebrates, and if you do your safety stop near one of the pinnacles you may be visited by shoals of reef fish including Hottentot, Galjoen, Dassie and Fransmadam. Relatively large numbers of Bank steenbras have been seen here, but mostly quite small. Zonation is variable according to depth and surface orientation. Some kelp above about 10m, but small and sparse. Red bait and other large ascidians fairly numerous, but not densely packed. There are patches of encrusting sponges and ascidians on relatively horizontal areas. Moderate numbers of elegant feather stars are scattered around. Common feather stars are also common in some areas, mostly where it is fairly steeply sloped. There are also clumps of red chested cucumbers, mauve cucumbers, striped anemones, Stephens' codium (relatively shallow), bushy corallines, encrusting corallines and Coral plocamium.

There are lots of gorgonian sea fans along the reef edges in the 15m to 20m depth range. Palmate, Sinuous, and Flagellar fans appear to be equally common. There are huge numbers of golden sea cucombers on the reef slopes to the north and more expectedly, also in the sand along the reef margins. Occasioanally virtual carpets of hairy brittle stars can be seen at the north end of the reef.


Good photographic site. Most equipment will be usable depending on visibility.


  1. Main Reef: Drop off over the main reef and work your way down to the sand, then back up to one of the pinnacles if the surge is not too strong.
  2. North Pinnacle: Either drop off over the North Pinnacle, or at the northern pinnacle of the main reef, and swim north over the sand to the North Pinnacle. After the dive either shoot a DSMB and ascend, or swim across the sand to the south and ascend at the northern pinnacle of the main reef.
  3. South Pinnacle: Drop off at the pinnacle, dive the reef and ascend at the pinnacle. This is a relatively small area, but enough for a good dive.

Stay safe


Great white sharks have been seen in the vicinity.


No special skills required, though the ability to deploy a DSMB is useful in case you are separated from the group or need to surface away from the shot line.


A light is useful to restore colour at depth, a compass to keep track of your movements, and a DSMB will let the boat know where you are when surfacing.

Back to Diving the Cape Peninsula and False Bay#Roman Rocks reefs

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