Difference between revisions of "Diving the Cape Peninsula and False Bay/Pinnacle"
Latest revision as of 05:14, 1 December 2010
This article is a travel topic
This site has very varied topography, which provides a large range of habitats, and these provide shelter for a large diversity of organisms. There are not many fish, but the invertebrates are unusually varied, and the site is accessible and relatively sheltered. Visibility is not often good, but there is a lot to see.
The pinnacle is a few kilometers south west of the last houses of Gordon's Bay.
This is not in a Marine Protected Area. A permit is not required.
Named for the rocky "Pinnacle" that breaks the surface just offshore at most states of the tide.
Maximum depth at this site is 14m, a few metres beyond the edge of the sand. The reef extends from about 12m at the edge of the gravel, to the surface along the shoreline.
Visibility is seldom better than 8m, and is more usually between 3 and 6m in summer. In winter it is often worse, and diving at this site is more often limited by visibility than by sea state. It can be dived when visibility is as low as a metre, but though there is still a lot to see, it may be difficult to find things. Visibility can vary significantly with depth. Some days it is quite good in the shallower parts, but drops off below about 9 or 10m where the fine silt tends to deposit.
Entry gully: The shore entry gully runs parallel to the general shoreline at the north east side of the cove. It is about 5m deep and the gully mouth bottom is rounded smallish boulders.
Cave: A small, narrow, shallow cave which extends about 15 metres straight into the cliff is accessible if the swell is very low. It is near the surface (max depth 3m) and strongly affected by surge as the free surface extends all the way to the back of the cave. The mouth is always visible, and the cave tapers slowly with a sudden end. This cave is round the left side of the entry gully mouth and is roughly parallel to the entry gully, following the bedding planes of the rock. Follow the left side rock face out of the entry gully and round the corner.
Outer gully: Outside the entry gully there is another gully, somewhat deeper, also parallel to the shore. The ridge to seaward of the outer gully does not quite reach the surface. This second gully is quite deep to the north east at more than 6m and is worth exploring. North west of this ridge the bottom is small rounded boulders to the pinnacle.
Pinnacle: The rock pinnacle which gives the site its name is just offshore from the entry gully in about 8m depth and is easily identified, as it breaks the surface at most states of tide. The pinnacle landward end is very sheer on both north-east and south faces, but tapers down more gradually to seaward.
Sponge rock: There is a large rock toward the south side of the cove with a spectacular orange wall sponge at the top, which is about 6m deep on top. It is about 50m offshore, at S34°10.490’ E18°49.959’, and the bottom is at about 9m. You can find it by following the 8 to 9m contour south-west from the pinnacle.
North west: To the north west of the pinnacle there is sand bottom starting at about 11m depth. There may be seasonal changes as sand covers the pebble zone, or is washed off to expose it again. There are isolated outcrops in the sand and pebble zones, but they have not yet been mapped. Most, if not all, are less than 2m high
North east: To the north east there are big outcrops on mostly low rocky reef. The shoreline has some deep gullies which continue below the water. In the area directly offshore of the steep part of the path there is a large rock which rises to about 3m from the surface. Further along the shoreline is a deep gully that extends several metres into the cliffside. This is the furthest extent of the Pinnacle dive site. Beyond this point is the south part of the Stone Dog section of Cow and Calf
Islet: There is a large rock (the islet) to the south west of the cave which extends above the water. If the conditions are very calm and the tide is high it is possible to swim around this rock, but the narrow strait to landward is shallow (and partly hidden by trees in the photo)
South west shoreline: Off the shore south west of the cove the deep bottom is flat parallel rock ridges with codium seaweed above the pebbles and sand. There is at least one large outcrop several metres high in this area.
Sand and pebble beds: The border between the sand bottom and pebble beds is quite far out in places, perhaps with seasonal movement. Tongues of sand in the pebble zone north of the pinnacle. possibly in a low area, and possibly seasonal, extend in towards the shore. The sand in the south west part is quite coarse and looks a bit shelly. The ripples were about 1m apart and the coarse sand seemed to form narrow parallel ridges on the finer sand beneath it. Further to the north east the sand is finer and the ripples more chaotic and much smaller.
Just inshore of the sand is mostly a zone of pebbles, seemingly of the sandstones of the area, well rounded and of approximately golf ball to tennis ball size, bedded in sand. The border between the sand and pebbles is very vague in places, and it may be that the pebbles extend under the sand for a considerable distance and are covered by a thin sand layer of seasonally variable extent. There are a few large (>1m) outcrops along this border.
There are extensive pebble beds and some fine sand directly offshore of the cove. Isolated rock outcrops up to 2m high are scattered about the sand and pebble zone. Fine grey silt may temporarily deposit on the sheltered side of outcrops in very calm conditions.
Geology: Light grey to yellow-brown quartzitic Ordovician sandstones, probably of the Graafwater formation of the Table Mounain group. Strike is roughly parallel to the shore, and dip is steep, in the order of 70° to the south east.
The site is partly exposed to south westerly swell, but well protected from south easterly winds. The site is usually at it's best in summer but there are also occasional opportunities in autumn and early winter.
This is an area which sometimes has red tides (summer), and poor visibility due to rain run-off (winter).
Keep a lookout for times when the south westerly component of the swell is low, and short period (10 seconds or less), and the wind is calm or from the south east, for a high probability of good conditions.
A long period swell from the south west will produce strong surge and usually poor visibility, and may make shore diving unacceptably hazardous. Assess the conditions from the roadside to the south, where the surge in the gully can be seen, before making the climb down to the entry area to make a close-up assessment.
If the swell is in sets, the access from the gully will be significantly affected, and if the swell picks up during a dive it is important to spend long enough waiting in the mouth of the gully to assess the best stage of the set to make your exit. Fortunately the surge movement at the exit area is largely vertical, and does not have a strong tendency to throw you onto the rocks at the inner end of the gully. This means that you can use the surge to lift you, but must then get out of the way before the next wave.
The paved off road parking is adequate, and there is a baboon proofed garbage bin, but no other facilities. Security is dubious, like any other local site along a public road.
Access is usually by boat, a short ride from Gordon's Bay harbour (3.1km)or Harbour Island (3.8km), but can be done as a shore dive by a fit and agile diver.
Boat access: Boats usually anchor to the south west of the pinnacle. The bottom is rocky and holding is uncertain. It is recommended that a crew member is left on board. Not a good anchorage in an onshore wind, but the diving will probably be unpleasant then too. It is worth starting the dive with a visit to the anchor to check that it has set correctly and will hold, but is not fouled and will be possible to retrieve after the dive. Try to avoid damaging the reef with the anchors.
A certain amount of scrambling is involved, moderately strenuous, but nothing difficult. Check out the route before kitting up as it is easy to take a wrong turn and this is better when not burdened by wet suit, cylinder and weights. The best known route is to the north of the inlet, with entry and exit in a south opening gully parallel to the shore, which provides good shelter and fairly easy entry and exit in good conditions.
The path down to the shore starts directly opposite the concrete garbage bin at the parking area. It goes more or less directly towards the sea, tending slightly to the right, and weaving amongst the bushes. The first important landmark along the path is a sandstone outcrop where the slope starts getting steep. Pass to the left of this, then once below it, move toward the right until directly below the steep rock. The path then proceeds more or less directly down to the start of the gully to the left.
Continue along the bottom of the gully over the small rounded rocks until you reach the water’s edge. The entry and exit point is a sloping ledge to landward of the main part of the gully, just beyond the last big boulder in the gully, and on the left hand side. Note that the surge can be awesome in a large sea.
The ridge on the left of the photo is not as steep as it looks, but not a place for bare feet or soft booties. The small black dot to the right of the gully mouth is the top of the pinnacle. On the seaward side of the ridge to the right of the gully is another submerged gully and ridge. The best point along the ledge for entry or exit will depend on the tide and surge at the time, and it is suggested that when the tide is low or the surge is strong, the entry or exit should be further to the south west near the mouth of the gully.
Various zones can be identified based on depth, exposure and substrate.
The shallower water to a depth of about 4 or 5m is dominated by dense encrustations of red-bait, a large sea squirt, and a large variety of other organisms which find the red-bait pods a congenial home. False corals and sea fans are most noticeable on the steeper sides of the reef in the deeper depth range, and sponges are more common with incresed depth. The smaller rounded boulders tend to be covered with encrusting sponges, hydroids, bryozoans and sea urchins, and in the shallower areas, a range of seaweeds.
Big sea squirts in the pebble zone provide a substrate for other invertebrates, and this is also the place to find tubular hydroids and burrowing anemones.
A wide range of nudibranchs have been seen here on a regular basis.
Spider crabs seem to be fairly common on sea fans in the deeper reef and pebble zone to the west of the cove. (offshore from Sponge Rock)
A small cavern just below the surface that extends a few metres into the rock. It has a free surface in a narrow crack which extends most of the way to the back, so the surge can be very strong.
This is a good site for invertebrate photography, particularly macro work, as visibility is seldom good enough for anything else. Use external flash for anything further than about 300mm away to reduce backscatter. Wide angle lenses can also produce good results on a good day.
Much of the marine life can be seen in the immediate vicinity of the pinnacle. If the sea is particularly flat the cave may be worth a visit if you like small narrow holes (big enough to turn around in).
Shore access requires a scramble down fairly steep rocks and a tricky entry and exit depending on swell. The path may be littered with broken glass. The cave may be unsafe if there is a moderate swell.
No special skills required. Night dives are best done from a boat as the climb is tricky in the dark. This is a popular site for training and for novice divers, also generally from a boat as the shore entry is a bit tricky for beginners.
A reasonable level of fitness is recommended for shore diving, as the path is rugged and steep. Walk down the path first and decide if you can do it in full kit.
A light is recommended if you intend to go into the cave, and can be useful for looking into crevices and for restoring true color. The site is fairly complex and a compass is useful to orientate yourself in conjunction with the landmarks.