Pie Rock reef and Outer Castle or Castle Blinder is an offshore rocky reef with a group of dive sites in the Castle Rocks restricted zone on the False Bay coast of the Cape Peninsula , near Cape Town in the Western Cape province of South Africa.
This is a spectacular dive in good visibility, and large numbers of fish may be seen. Outer Castle is structurally, topographically, geologically, and by most other considerations part of the same reef, but was historically considered a separate site. The southern part of the site was known by the name "Pie Rock" before 2004. The sections were named after mapping started and eventually it became obvious that Outer Castle is the northern part of the Pie Rock reefs,
Outer Castle is a blinder about 600 m east of Castle Rocks, which breaks if there is much swell, and is then visible as a patch of white water
North Pie Rock pinnacles are about 760 m from the north entry area at Castle Rocks. Bearing 353° True (017° magnetic) to Bakoven Rock, approximately 278° True (302° magnetic) to north side of Castle Rocks, and about 150 m south east of Outer Castle, There is an iron anchor to the east of the main pinnacles at about 18 m depth at S34°14.381' E018°29.105'
South Pie Rock Pinnacles are in the extreme southern part of these reefs, nearly directly south of the North Pie Rock area, on a distinct lobe delineated by sand tongues to the east and west, and sandy bottom to the south. The western reef is inshore of the south pinnacles, and there is an deeper lobe of reef to the east, called East Pie Rock Reef. There are other nearby reefs across sandy gaps of varying widths. Some have been explored, others may never have been dived.
This site is in a Marine Protected Area (2004). A permit is required. The sites are entirely inside the Castle Rocks Restricted Zone.
The northern section is known as "Outer Castle" or "Castle Blinder" due to its position off Castle Rocks. It is marked on the SAN charts as “blindevals”, The rest of the area was called "Pie Rock" because one of the larger rocks in the area is said to look a bit like a giant wedge of pie.There does not seem to be any record of which rock this is, but the name stuck. The names for the central and southern parts of the reef were given as descriptions to identify them by relative position. Outer Castle was known by that name and dived on in the 1980s and probably earlier. It is visible from the shore as a blinder, a submerged rock which causes waves to break over it in some sea states and tides. It is offshore of Castle Rocks, a distinctive granite promontory, which is reflected in the name.
Maximum depth is about 25 m at the sand to the east. The top of the Outer Castle blinder at less than 3 m, is visible from the surface on a good day. Top of the highest pinnacles of the Pie Rock sectors is at 4 to 5 m. Average depth on a dive is about 15 to 18 m, within the range for entry level divers.
Visibility will be similar to the nearby reefs, but may be a bit better than on the inshore reefs because there will be less surge on the sand, and the deeper parts may be below the worst of a plankton bloom or offshore of rain run-off.
Large granite corestone outcrops and boulders. The site is in five main sections, Outer Castle, Pie Rock North Reef, Pie Rock Southern Pinnacles, Pie Rock West Reef and Pie Rock East Reef. Each of these sections is distinguished from the rest of the reef by having local high areas or pinnacles, with deep areas and sand-bottomed gullies between them to some extent, though there is continuous reef connecting all the major lobes. Most of the reef is contiguous, but there are a few outliers and relatively small separate areas.
Geology: Granite of the Pre-Cambrian Peninsula pluton, surrounded by sand.
The site is moderately protected from south westerly swell. South east chop may make it unpleasant on the surface, but it may be quiet below the wave base, however a strong south-easter or one that blows for a long time will push up a swell that will make it unpleasant all the way down. Generally considered a late autumn and winter dive site but there are also occasional opportunities in other seasons. A north-westerly wind can raise a chop that can make the boat ride back wet and uncomfortable, though it is unlikely to adversely affect underwater conditions.
Outer Castle is diveable if there is no break on the reef, and in many cases even if there is. A long low south westerly swell may produce surge and a small break over the top, but may be otherwise quite pleasant conditions. Generally considered a winter dive site but there are also opportunities at other times.
The site is generally considered a boat dive. It is approximately 2 km from Miller's Point slipway and 9.3km from Simon's Town jetty. It could be dived from shore entry at Castle Rocks, but would require a 750 m swim each way. For a shore dive use a SMB when near the surface, as boat traffic in the area can be heavy on a good day. Bearing from Castle Rocks north entry approximately 120° magnetic. Don't try this in a strong offshore wind.
Outer Castle can also be dived from a shore entry at Castle Rocks, but this requires a 600 m swim each way. Use a SMB as boat traffic in the area can be heavy on a good day. Bearing from Castle Rocks north entry approximately 027° magnetic. Easiest to find with GPS, but if the tide is low the waves may be seen to pick up and occasionally break. If there is a prominent break the site may not be pleasant to dive, and may be dangerous. The Pie Rocks reefs could also be dived from the shore entry, but finding the pinnacles would require a GPS.
Dive at one of the drop points listed here, and explore the local reef around each point,
- 1 Outer Castle: S34°14.321’ E018°28.994’ – The main feature of the section is a huge granite boulder on a rock base standing on four points with a swim-through gap underneath. There is a small air cave at about 9m depth on the west side, known as Anton's oven. This is easy to find as it is marked by a deep groove in the west side of the rock which extends from about 7m deep right down and under the rock. The air cave is a part of this groove. The boulder is about 40 m long on a north-south axis and 15 m wide. The maximum width is at 6 to 9 m in most places and below that is overhang to a greater or lesser extent, which eventually curves right under the rock into the swimthrough area. Above the 6 to 9 m range, the upper part of the rock curves away to the top, which is probably about 3 m deep at low tide, but is usually in an area of extreme surge or white water. A short distance to the north there are a few large boulders reaching up to just above 12 m, and a short way beyond them, the reef borders on sand at a depth of about 18 m. The reef perimeter to the north runs roughly east-west. and the next reef system to the north is quite along distance away. To the south, the reef is contiguous with the other parts of Pie Rock reef, which starts about 50 m to the southeast at Pie Rock North Pinnacles, and extends for a few hundred metres to the south and east. Directly to the east of Outer Castle pinnacle the reef is relatively low, with a few odd boulders and outcrops reaching up to 12 m, and to the west the reef is more or less continuous all the way to the Castle Rocks point, interrupted by moderate sized sand gaps and sandy bottomed gullies, depending on exactly which route is taken.
- 2 North Pie Rock: S34°14.375' E018°29.075':– Pie Rock North Pinnacles is two adjacent groups of high pinnacles south of the Outer Castle blinder. This is the central part of the Pie Rock reef complex, and the northernmost area referred to as Pie Rock. It is the first of the Pie Rock reefs to be recorded as a dive site, and the early dives were probably mostly near the eastern sand edge of this area. A large part of this area is above 15 m.
- 3 West Pie Rock Reef: S34°14.396' E018°28.943':– Pie Rock West Reef is a relatively shallow area west of the north and south pinnacles, with a shallow point at about 4 m depth, a large area above 12 m, and almost all the rest above 15 m.
- 4 East Pie Rock Reef: S34°14.432' E018°29.153':– Pie Rock East Reef is a partly explored area to the south-east of the north pinnacles. Early survey indicates fairly open reef extending to at least 25 m depth to the southeast, with some pinnacles rising to about 12 to 18 m depth to the east and southeast. Much of the reef is below 18 m and remains unexplored. The edges are a bit diffuse, with sandy indentations and patches among the rocks, and rocky bits in the sand. There is a swimthrough under a boulder pinnacle on the southeastern reef edge.
- 5 South Pie Rock Reef pinnacles: S34°14.445' E018°28.985':– Pie Rock Southern Pinnacles are part of a more extensive area of low reef to the south, with a picturesque group of shallow pinnacles rising to about 4 m depth at the shallowest point, and a fairly large area above 15 m.
The top of the rock at Outer Castle is heavily colonised by the Red bait ascidian, and some kelp. Below the line of maximum width, a larger variety of invertebrates may be seen. Large numbers of false corals, feather stars, colonial ascidians, red sea cucumbers and colonial hydroids. A reasonable variety of fish, sometimes in fairly large shoals. The site is in the Castle Rocks Restricted Area, which is the best region of the Cape Peninsula and False Bay for observing fish, though poaching does occur and enforcement is very sketchy at best.
Typical invertebrate encrustation at Outer Castle
Sea urchins and Red chested cucumbers
Diver and seal at Pie Rock
Blue choirboy ascidians
Orange clubbed nudibranch
Red chested sea cucumbers can reach a high population density
Scallops can occasionally be seen on the sand
Swim-through under the rock at Outer Castle, and a small air-trap overhang half way up the inshore side.
Like most of the dive sites in this part of False Bay, the visibility is not very predictable, and in most conditions close up and macro photography will be a good choice. Wide angle scenic shots can give good results when the visibility is unusually good. For close up work some form of artificial lighting is advised, both to reduce blur by shortening exposure time, and to bring out the colour.
No particular routes recommended. Start deep, at Outer Castle, visit the swimthrough under the rock and the little air trap on the shoreward side at about 9 m depth (do not breathe the air, it may be low on oxygen). The surrounding reefs are worth a visit if you have the time. Work your way up and around the sides of the rocks. The pinnacle areas are small enough to visit each on a single dive, but there is a lot of surrounding reef.
Offshore wind may increase in strength significantly during the dive, which can be a problem for shore dives if you need to return on the surface. This is an area where boat traffic may be heavy.
Certification appropriate to the depth is expected, otherwise no special skills are required for boat dives. Ability to deploy a DSMB may be useful if you surface away from the shotline. Ability to navigate using a compass and fitness to swim the distance are required for a shore dive.
A surface marker buoy is recommended for shore dives as there is often boat traffic between the reef and shore. A compass is virtually essential for shore dives as it will be needed both to get there and find the site, and to navigate back. A light is useful for looking into small holes and when under the rock to illuminate the organisms on its surface. Nitrox will allow extended time for no-decompression dives, and would be particularly useful on a shore dive as it would allow a deeper return swim, where you can see the reef. A DSMB may be convenient for a boat dive if you surface away from the shotline.
- 1 Miller's Point tidal pool
- 2 Murphy's
- 3 Boat Rock
- 4 Festival Pinnacle
- 5 Fan Reef
- 6 Shark Alley
- 7 Pyramid Rock
- 8 Phone reef
- 9 Giant's Castle
- 10 Zigzag Reef
- 11 Castle Rocks Point Reefs
Back to the Alphabetical list of sites, or list of dive sites in the Castle Rocks area
Other regional dive sites: