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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 of the lighthouse


  • S34°10.60’ E018°27.56’ (North reef pinnacle)
  • S34°10.68’ E018°27.59’ (Castor reef northern pinnacle)
  • S34°10.74’ E018°27.61’ (Castor Rock central pinnacle)
  • S34°10.81’ E018°27.65’ (Wonders pinnacle)
  • S34°10.831’ E018°27.802’ (Roman's Rest pinnacle)

An extensive area of rocky reef north of Roman Rock lighthouse with several pinnacles

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. There are a few other pinnacles above 12m.


This is an extensive reef of granite. Basically a very large area of moderate to low outcrops 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.

The reef is divided into two large lobes by a pair of narrow sand tongues which encroach into the reef from the east and west, and nearly meet just north of Wonders Pinnacle on the west side of the south lobe.

The northern lobe is Castor Reef proper, and is more compact and substantial overall than the southern lobe. The edges are also penetrated by gullies, but to a lesser extent. The northern end is relatively flat and slopes gradually down to the sand, but the eastern and western sides are more ruggedly profiled. Castor rock reef north lobe 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.

The pinnacle to the north east is Castor Rock pinnacle, which is a locally shallow area with a steep drop to the sand on the north east face, and more gradual slope to the reef top on the other sides

There is a high profile reef section 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.

The southern lobe is longer and narrower than the north lobe, and has an area of pinnacles at each end. The reef between is lower and somewhat broken along the edges. This lobe is also known as Wonders Reef.

The western pinnacle is Wonders Pinnacle, and the eastern area is Roman's Rest pinnacles. The main pinnacle of Roman's Rest is a huge outcrop rising from the sand to just above 12m at the top, very steep on the north east side, and with several deep round bottomed indentations. The east side is also pretty steep, but the south west side is more gradually sloped and the north west side steps down towards a pair of lesser pinnacles to the north west. These are huge boulders standing on a flattish rock base at about 20m depth and rising to about 12m at the top. One of them is relatively narrow for its height, about 5m one way and about 7 or 8 the other way, and is about 8m high and pointed on top. The other is wider and a bit lower, but they make an impressive pair. They can be seen from the edge of the sand tongue in reasonable visibility.

There are occasional low outliers around the east end of the reef near the pinnacle.

Castor reef has several other reefs nearby which are known as good dive sites, These include Roman Rock, Tivoli Pinnacles, Friskies Pinnacle and the Rambler Rockreefs.

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[edit]

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

See[edit][add listing]

Marine life[edit]

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[edit]


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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