Diving the Cape Peninsula and False Bay/Rocky Bay
S34°11.585’ E018°49.035’ (Anchorage — very approximate, almost anywhere will do)
S34°11.393' E018°49.113' (Gully entry point for shore dive)
Rocky Bay is just off the resort on the shore to the north of Steenbras River mouth.
This site is NOT in a Marine Protected Area. A permit is not required.
This is not actually a bay at all. The coastline has a convex curve along this dive site. The resort on the shore is called "Rocky Bay", and the site name follows from that.
Depth is about 21m at 200m offshore and the bottom further out is very flat, dropping to 27m about 600m offshore.
Visibility is usually quite poor — 5m would be considered good for this site — as there is usually some surge disturbing the bottom. Visibility appears to usually be less than 3m and may easily be as low as 1m or even less. However it may not be as bad further offshore, and if it is bad where you descend, try swimming west a few hundred metres.
Sandstone ridges and gullies roughly parallel to the shore line, which is steep and reflects rather than breaks waves, so the anchorage is very bumpy in a swell. The entry gully is deep (about 10m) and outside are irregular sandstone ridges approximately parallel to the shoreline. This area gets fairly deep quickly, then slopes gradually down with outcrops getting lower and more sparse with distance from the shore. There are considerable areas with coarse gravel, but hardly any sand even between ridges. Further out (about 50m offshore) the bottom is gradually sloped, with moderate size ridges and outcrops. Even further offshore it gets flatter with low rocky reef and pebbles and small boulders. There is no sign of large sandy areas down to 21m. Occasional larger ridges are scattered in no discernable pattern.
The bottom from about 200 to 400m from the shore is small boulders/shingle, but apparently quite stable, as the stones are covered with extensive and well established encrustations of invertebrates. Further out the bottom changes again to low bedrock reef, but the type of rock appears different, and the strike looks like it runs east west, with a steep dip, but it is not easy to confirm these details as the reef is pretty flat, not more than 1m profile height. It may be that this is the underlying Tygerberg formation. There are large patches of sand beyond about 400m offshore, but no definite end has been found for the reef.
The river bed is sandy under the bridge then rocky further out, with medium to small boulders, getting bigger with increasing depth. The east corner of the mouth has big boulders and outcrops and a lot of powerful surge, even in a very low swell. It gets deep quite rapidly to about 8 or 9m, then more gradually over a bottom of ridges and gullies, some with sandy bottoms, mostly running approximately parallel to the coastline. Some way out is a set of bigger ridges, with red bait on top and a relatively large variety of species, including some nice gorgonians. Further out it gets gradually deeper and gradually less rugged, in the same basic pattern.
Geology: Ordovician sandstone of the Table Mountain group, probably Peninsula formation, but possibly the underlying Graafwater formation. Further out it may be Tygerberg formation. Strike of the inshore strata is approximately parallel to the shoreline, and dip about 30° to the north east. Further out it appears to be different.
The site is exposed to south westerly swell, and moderately protected from south easterly winds. The site is usually at it's best in early summer but there are also occasional opportunities in autumn and early winter.
This is an area which sometimes has red tides in summer, and poor visibility due to rain run-off in 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 moderate 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 north, where the surge in the gully can be seen, before making the climb down to the entry area to make a close-up assessment.
None. There is no convenient parking nearby, and you have to find a spot along the edge of the road where you can pull over without obstructing the road or falling down the mountainside.
 Get in
Boat dive: From Gordon’s Bay or Harbour Island. Anchoring is possible off the cliffs in front of the resort houses in about 15m to 20m depth. Stay far enough offshore to avoid the worst of the reflected waves.
Shore dive from the gully: Park on the verge of the seaward side of the road above the inlet to the north east of the resort at Steenbras River mouth. It is quite a hike down to water, but not difficult. The path is not obvious, so make a reconnaissance before kitting up. Entry is in the inlet closer to Steenbras mouth which has much less surge than the one nearer to Gordon's Bay.
Shore dive from the river mouth: Park on the side of the road as near to the bridge as legally possible. Entry is under the bridge. Walk down the path upstream of the,bridge or down a steeper but fairly stable path right next to the road also on upstream side. The water may be shallow and you may have to wade for about 50m before it is deep enough to swim.
[add listing] See
 Marine life
Basket stars have often been seen on the deeper reefs. Galjoen in the inshore gullies, and a good range of invertebrates on the reefs.
The shingle bottom looks pretty stable, with well established benthic encrustation. Lots of Peacock fanworms about 200m offshore, not so many further out. Solitary squirts of a few species, common feather stars, golden cucumbers, encrusting sponges, a very few small sea fans.
Further out: lots of pore-plated false corals, particularly the pale grey lacy one, the dark brown one and the heavy orange one. A few klipfish, anemones and tube worms. A small amount of encrusting corallines, but no other seaweeds recorded.
This is a good area for invertebrate photography if the surge is not too strong. (photographic equipment suggestions)
 Stay safe
No site specific hazards have been reported. Shore access at the gully requires a walk down steep rocks and a slightly tricky entry and exit.
No special skills required. Moderate fitness and agility is required for a shore entry.
A compass may be useful for orientation, and a SMB will help the boat keep track of divers. Nitrox will be useful to those who like a long dive.