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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 a 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. Information is provided which may assist in planning Recreational and Research Scuba diving at this site, and links to photographs of marine organisms that have been found there.

(reasons to dive at this site)

Name "Castor Rock"

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

File:(insert image file name)
Map of the dive site (Insert site name).


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 (2009)


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


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. Poor visibility at the surface does not necessarily extend to the bottom.


Maximum depth is about 18m to the south, and 20m to the north. The highest point on the reef is about 4m deep.


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


This is an extensive reef of granite. Basically a very large outcrop with occasional high areas, small gullies, boulders, small crevices and overhangs. 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. 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, between Castor Rock and Roman Rock that is reported to be a good site.


Great white sharks have been seen in the vicinity.

Skill level

No special skills are required. The ability to deploy a DSMB is recommended.


Good photographic site.


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.

Marine life (and features)

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. 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.

Suggested Routes

  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.



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