Difference between revisions of "Diving the Cape Peninsula and False Bay/Atlantis Reef"
Latest revision as of 17:25, 1 May 2012
The dive site Atlantis Reef or Pillars of Hercules is an offshore rocky reef in the Finlay's Point area of the Castle Rocks Restricted area on the False Bay coast of the Cape Peninsula, near Cape Town in the Western Cape province of South Africa.
The first GPS survey of the reef places it on one of the sections identified by the Council for Geoscience side-scan survey of 2011.
The site name was chosen by the first divers to report diving at the site. It is named after the legendary lost continent of Atlantis from Greek mythology.
Maximum depth is about 29m at the eastern limit of the reef, and the top of the highest pinnacle is about 4m deep. Average depth on the immediately adjacent reef is likely to be about 20 to 25m.
Visibility can vary like any other dive site in the area, but in diveable conditions is likely to be between 5 and 10m, and on a very good day, up to 20m. It is generally similar to, but often not quite as good as visibility on the Smitswinkel Bay wrecks
The site is dominated by a pair of massive pinnacles, which rise from a jumbled mass of boulders below 18m to within 5m of the surface. The tops of the pinnacles are relatively small and rounded, and are probably in the order of 3m diameter, but they spread out to 15 to 20m wide with roughly rectangular plan at 12 to 15m depth. These have been named the "Pillars of Hercules, in keeping with the Greek mythology theme. On the western and southern sides of the eastern pinnacle there is a large overhang. The granite base between the two pinnacles has a deep crack in it, and to the offshore side of the pinnacles, there is a complex swimthrough formed by jumbled boulders. There is a ledge to the north at about 18m, and a number of very large boulders in the immediate vicinity to the north. A fairly large rock with a pointed top at about 17m known as the "Fang" stands a few metres to the east of the pinnacles. It is shaped a bit like a large canine tooth. There is sand a few metres to the south of the pinnacles at about 24m depth.
To the east of the pinnacles the reef edge comprises medium to large outcrops of granite corestone, with sand between them in the gaps. The reef tends to get lower to the north and more broken to the north west, where large areas are quite low and made up of small boulders and low outcrops.
South east of the pinnacles there is a large outcrop a few metres high which has a dense growth of Sinuous, Flagellar and Palmate gorgonian sea fans.
150m on a bearing of 145°magnetic from the western pillar, there is another somewhat lower pinnacle, rising to 10m depth. This and the smaller pinnacle another 30m to the west have been named the "Santorini pinnacles". They are not as spectacular as the Pillars of Hercules, but are a good divesite in themselves, with plenty of steep walls and overhangs to shelter the reef life.
Geology: Pre-cambrian granite of the Peninsula pluton, with fine silica sand in the deeper areas and around the reef.
The site is often at its best during or after a westerly wind, but may be good even during an easterly if it is not too strong and the swell has not built up yet. Surge may be considerable in long period swell even if low.
The site is exposed to south east wind and waves, and is moderately exposed to south westerly swell, particularly long period swell, which bends round Cape Pointthough Atlantis is not far to the north of the reefs at Partridge Point, and they provide some protection from south-westerly swell. The site is usually at its best in winter but there are also occasional opportunities in autumn and spring, and sometimes even in summer a good day may occur.
Look for days when the forecast is for swell from the west, or low swell from the south-west. This can often occur just before a cold front gets to the peninsula, and in these cases the weather is often mild, even sunny, and with little wind in the day or two before the front arrives. During the passage of the front, the weather is generally windy, overcast and frequently rainy, but may still provide very good diving if the wind is not too strong for the boats to operate, as it will be offshore until the front has passed.
After the front has passed, in winter one can expect a day or two of good diving before the next front. In summer, a front is commonly followed by strong south easterly winds, which kick up an unpleasant short onshore chop which makes the boat ride uncomfortable and messes up the visibility.
This is a boat access dive site. It is technically possible to dive it from the shore, but there would be a long steep climb down from the road to the shore on a slippery path, followed by a long surface swim. Then you would have to find the site, which in itself is not easy.
The site is about 3.2km from Miller's Point slipway.
The marine life is extensive and varied. At the tops of the pinnacles and extending to about 12m is a heavy covering of red bait with both knobbly and false plum anemones living in between them. Descending the pinnacles, the more delicate invertebrates take over and the pinnacles' lower sections are densely covered with bryozoans of at least five different species, and a heavy covering of multicoloured seafans. Between the pinnacles is usually found a school of several species of fishes: blacktails, hottentots, fransmadam and zebras. Moderate numbers of bank steenbras have been seen on the western part of the reef. Nudibranchs such as the black, the crowned and gasflames are common on the pinnacles, with the occasional sighting of smaller nudis such as the orange-eyed nudi and the white-edged nudi. Janbruins can often be seen in the cracks between the pinnacles, and there are somevery large Roman.
Where the reef at the base of the pinnacles meets the sand to the south, the lower parts of the reef are covered with red-chested sea cucumbers, strawberry anemones and nippled sea fans. North from the pinnacles in the jumbled boulders is a luxuriant seafan forest, consisting of palmate, sinuous and whip seafans. The usual assortment of invertebrates associated with seafans can also be found: topshell snails, hermit crabs and basket stars in abundance. Further north on a lower profile reef section there is more seafan forest which is sometimes overwhelmed by hairy brittlestars to the extent that it resmbles an afghan rug. The sand at about 29m seems to be a shyshark nursery because many small puffadder shysharks can be seen there. Interestingly, the site also features an unusual number of dark shysharks, more usually seen on the Atlantic side of the peninsula.
Notable features of the site, apart from the Pillars of Hercules include the systems of swimthroughs formed by the jumbled boulders at the base of the site and the site's overall topography. Fang-shaped boulders, vertical cracks, embayments of sand, small drop-offs and overhangs are all worth viewing.
Good wide angle scenic shots can be taken in conditions of good visibility. The reef life is diverse and prolific, and there are opportunities for both macro photography of benthic organisms, and wide angle photos of the shoals of small fish. The site has been praised as a photographic destination by several notable local underwater photographers, and frquently features on the Facebook site "Underwater Cape Town".
No special routes are known at this stage, but the pinnacles are the highlight of the site, and the dense gorgonian forests on the edge of the reef slightly to the south east of the pinnacles are well worth a visit. The area near the pinnacles appears to be the most topographically interesting, so explore the area, and let us know what you find.
No special hazards are known.
Certification to dive to the depths found at the site would be expected. Parts of the site are within the depth range appropriate for entry level divers, but not very much, and because the site is so pristine, it is recommended that entry level divers and others with imperfect buoyancy control avoid diving there.
No special equipment required. Divers who intend to explore beyond the vicinity of the pinnacles are advised to deploy a DSMB at the end of the dive so the boat can see where they will be ascending.