The dive site Roman Rock is an offshore rocky reef in the Simon's Bay area on the False Bay side of the Cape Peninsula, near Cape Town in the Western Cape province of South Africa. This site includes the small outlier Spider Crab Reef to the south-west of Roman Rock.
This site comprises a cluster of huge outcrops separated by sand bottom, on one of which the lighthouse stands.
Roman Rock reef is part of the Roman Rock reef complex offshore in Simon's Bay on the west side of False Bay. This is an extensive area of granite reef, much of which is inside the Boulders restricted zone of the Table Mountain Marine Protected Area. It is a topographically rugged reef, with exposed rocks and a few other very shallow areas, and extends down to a sand surround. The reef complex has several large reef areas, of which this is the south-westernmost, and a large number of smaller reef sections and isolated rock outcrops. The marine life is quite varied, though echinoderms are dominant, and a moderate variety of reef fish can be seen.
The site is popular when launches are made from the False Bay Yacht Club, as it is conveniently close. The reef is prominently marked by the exposed rocks and the lighthouse — You can't miss it...
- S34°10.87’ E018°27.60’ 1 Roman Rock. An easy dive site to find as it is marked by the lighthouse of the same name off Simon’s Town Harbour.
- S34°10.89' E018°27.43' 2 Spider Crab Reef
This site is in a Marine Protected Area (2004). A permit is required. The site is entirely inside the Boulders Restricted Zone.
There are several places on the South African coast known as "Roman Rock", and Roman Reef, and it is probable that they are all named after the common reef fish, the Roman Chrysoblephus laticeps.
Maximum depth is on sand at about 18 m. The top of the reef breaks the surface in places. The eastern part of the reef has a greater depth range than the western part.
Visibility is variable, and is unlikely to differ greatly from other nearby sites. 10m would be considered good, 15 m excellent, and 4 to 6 m marginal. The offshore reefs are less affected by south easterly winds than those closer inshore, as the sand bottom is too deep to be affected by wind chop, and the limiting factor in a south easterly wind is often surface conditions rather than visibility.
Flat coarse shelly sand bottom at 15 to 18 m with large granite corestones. Very large boulders and outcrops extend over a fairly large area, with deep gullies and high ridges. Dramatic relief. Two large rocks break the surface and support the lighthouse structure and a small helipad. The long axis of the reef runs roughly southeast-northwest and the main reef is about 400 m long and 110 m wide north to south, with the widest point to the east of the lighthouse. The Eastern part of the reef is very high profile, and extends from the sand to shallower than 3m in several places, though the extreme southeast part slopes more gradually. The western section is demarcated by a deep gully opening to the south, with sand bottom extending some way across the reef, which nearly disconnects the shallower western section from the eastern section. Minimum depth of the western section is about 10 m, and much of it is deeper than 12 m. There is a smaller ridge of reef approximately parallel to the main reef about 20 m away to the north east of the north west end of the main reef, and a few unsurveyed patches nearby.
Some distance to the south west there is a small patch of reef called Spider crab reef, so named as a relatively large number of spider crabs were seen on the day the reef was surveyed. The top of this reef is flattish at about 16 m depth, and it extends about 100 m from north west to south east and is about 20 m wide. The eastern and western of this reef consist of relatively small and low outcrops, with narrow sandy gaps between them.
Geology: Granite corestone outcrops and boulders of the late Pre-Cambrian Peninsula pluton, surrounded by whitish quartz sand, with a varied amount of shelly debris.
This site can be dived any time of the year that has low or short period swell. Poor visibility at the surface does not necessarily extend to the bottom. 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. The site is usually at it's best in winter and spring.
This site is always dived from a boat, though Navy divers in training were traditionally required to swim back to the base from this area, The site is 3.3 km from Simon’s Town jetty or the yacht club, and 5.6 km from Miller's Point slipway.
The rocks are encrusted with a variety of organisms depending on depth and orientation. There is kelp and sea urchins on the tops in shallower areas, and Red-bait and other large solitary ascidians scattered around. The steeper sides are largely covered by common feather stars, with some dense areas of mauve sea cucumbers on the tops of ridges, There are also occasional sea fans, some quite large. The sand is coarse and shelly near the rocks, and there are sand stars, brittle stars, sand slugs, cerianthids and purple sea pens on the sand. Dense aggregations of the Spiny starfish can sometimes be found.
The top of Spider crab reef is covered by large black mussels and quite a lot of spiny starfish. The deeper parts and sides are more typical of the area, with patches of mauve sea cucumbers, common feather stars, strawberry anemones and encrusting sponges. There were large numbers of hairy brittlestars on the reef and serpent skinned brittlestars on the sand. There are also a moderate number of sea fans and striped sea anemones.
This is a good photographic site. Macro or wide angle lenses are suggested.
There are no recommended routes. Start deep and work your way along the base of the rocks, slowly ascending and preferably surfacing from the top of a high outcrop if there is not too much surge.
Great white sharks have been seen in the vicinity. In windy weather a diver on the surface may be difficult to see from the boat due to choppy waves.
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, a DSMB to let the boat know you are surfacing, and Nitrox can extend no-decompression time significantly in this depth range.