Diving at Rocky Bank

The dive site Rocky Bank is an offshore rocky reef in the mouth of False Bay, near Cape Town in the Western Cape province of South Africa.

Understand

See also: Diving the Cape Peninsula and False Bay#Understand

This site has a different ambience to other Cape Peninsula and False Bay sites, and may have better visibility much of the time. The reef is spectacularly colourful in artificial light, and may have better visibility over a wider range of surface conditions, but has not been dived enough to be reliably predictable. It is a long boat ride, and the risk of getting lost at sea in rough conditions may not be acceptable.

Position

1 Rocky Bank: S34°24.93' E18°35.50' (arbitrary nominal position)

This site is not in a Marine Protected Area (2004). A permit is not required.

Name

Divers over Rocky Bank

Sponges, ascidians and other encrusting invertebrates at Rocky Bank

The name "Rocky Bank" is recorded on the SA Navy charts of the area. It is also a simple description of the area which is a bank of hard sandstone, mostly between 25 and 30 m deep on top.

Depth

The top of the bank is at about 22 m. The chart suggests that the area shallower than 30 m is about 2 square kilometres, and it slopes down gradually to over 100 m to the south. Most dives reported have been in the 25 to 30 m depth range. It has been difficult to find shallower areas due to the general flatness of the bottom.

Visibility

The bank has not been dived extensively, but there are indications that the visibility is usually better than average for the False Bay region, as the bottom is rocky, there can be a current, and the water is fairly deep and quite far from the coast, so waves will not easily disturb any sediment, and the current would carry it away rapidly. Visibility has been reported at between 10 and 20 m at the bottom. Algal blooms may reduce visibility near the surface to less than 5 m. Visibility can be good to excellent (over 15 m) on days when the inshore dive sites are murky, and even Whittle Rock is mediocre. Possibly the Cape Town dive site with the most consistently good visibility.

Topography

This is a large area, and probably varies considerably from place to place. Reports indicate that a large area is moderately flat hard sandstone reef with low dip angle, so there are steps rather than ridges. However there are areas with profile in the order of 2 to 3 m gullies and ridges. The bank is mostly between 25 and 30 m deep on top, gradually sloping down in all directions, with the deepest adjacent areas to the east and south, remaining somewhat shallower to the west and north.

Divers have found it difficult to find the shallower areas due to the general flatness of the bottom. There is no general uphill trend discernible, so one finds local rises of a metre or two, then it slopes down again. Southern areas may have higher profile than northern areas, but the sample is not big enough to establish a trend.

Geology: Sandstones, probably of the Table Mountain series. Strike direction is unknown, Dip direction also not known and fairly flat.

Conditions

The site is exposed to wind and waves from all directions, and the prevailing south-westerly open ocean swell is not greatly attenuated by the bottom when it reaches the bank, so should be dived in reasonably calm conditions. This may occur at any time of the year. Use the sea state and weather forecasts for planning. A choppy sea will give a long, slow, uncomfortable ride in both directions.

Get in

See also: Diving the Cape Peninsula and False Bay#Boat dives

This site is only accessible by boat. It is about 24 km from Miller's Point slipway, 31km from Simon's Town Jetty,or 37 km from Gordon's Bay Old Harbour.

Do

Dive at one of the drop points listed and explore the vicinity, or choose another point and see what you find. Most of the reef is unexplored, and though most of it has been surveyed by multibeam sonar, the images have not yet been published. The listed points indicate depth at the point. Depth does not usually vary much within a reasonable distance as the reef is not very steep overall and profile is moderate to low in most places.

1 22m drop: S34°24.820’ E018°35.473’

2 25m drop: S34°24.906’ E018°35.478’

3 30m drop: S34°24.957’ E018°35.473’

4 32m drop: S34°24.994’ E018°35.463’

5 36m Pablo's Steps: S34°25.126’ E018°35.756’. Drop onto about 36m and travel northwest up a series of low steps.

6 40 to 50m Rocky Ridge: S34°24.941’ E018°36.512’, A long east–west gnarly drop-off about 5 to 8 m high, with heavy encrustation of noble corals and sponges on the wall About 40 m deep on top of the ridge and about 45 m on the bottom, maximum depth about 50 m.

7 45m Ahmed's Bluff: S34°25.392’ E018°35.841’, a low bluff structure at about 45m, dropping off to about 50m.

8 50m North East Buttress: S34°23.842' E018°36.829’, a magnificent buttress about 45m on top dropping off steeply to 60 m Big walls, overhangs and lots of noble coral.

Routes

The site is vast and large areas are not distinguished by any notable features. No routes are known yet – find a place of suitable depth and do a drift dive.

See

Typical reef life at Rocky Bank. The foreground is illuminated by the camera flash and is what one will see in artificial light. The background is how it looks in natural light.

Basket star on sponge

Fan hydroid at Rocky Bank

Marine life

See also: Diving the Cape Peninsula and False Bay#The marine ecology

The rocks are encrusted with a large range of colourful sponges, ascidians, soft corals, noble corals, hydroids, and coralline algae. Shoals of small fish, and larger yellowtail swim over the reef, and occasionally sharks will be seen. The reef has more the feel of a South Coast reef than a False Bay reef, because the invertebrate assemblages have a different character. The character of the reef life varies with depth and reef profile, but this has not been reliably analysed in detail.

Photography

If the visibility is good, almost any equipment should produce good results. Natural light will be blue or green due to the depth, so a strobe or other artificial light will be needed to bring out the bright reds, oranges, and yellows.

Stay safe

See also: Diving the Cape Peninsula and False Bay#Stay safe

Hazards

Strong winds may develop over a short time. The site is far out to sea, it may be difficult for the boat to see unmarked divers on the surface. It is a long ride both ways, so protection against the weather and sun are strongly recommended on an open boat.

Skills

The ability to deploy a DSMB is recommended. For the deeper sites Trimix is recommended. On decompression dives it is prudent to dive in a group and stay together during decompression.

Equipment

See also: Diving the Cape Peninsula and False Bay#Equipment

Take the most powerful light you have to bring out the true colours. The natural light is very blue due to the depth. Each group leader should tow an SMB to allow the boat to keep track of their position. Each diver should carry a DSMB or other brightly coloured signalling device that can increase visible height by at least a metre (yellow is considered most visible at sea). A whistle may also be useful in an emergency. A personal locator beacon could be helpful if the conditions deteriorate and the boat has difficulty finding you.

Nearby

Other offshore dive sites of False Bay:

• 1 Choirboys Reef
• 2 Seal Island
• 3 Drop Zone
• 4 East Shoal
• 5 Moddergat
• 6 Sterretjies Reef
• 7 York Shoal
• 8 SAS Fleur
• 9 Offshore Barges – North Barge
• 10 Steenbras Deep - South Pinnacles
• 11 Blue Flame Pinnacles
• 12 SATS General Botha
• 13 Off-Whittle Ridge
• 14 SAS Bloemfontein
• 15 Whittle Rock
• 16 Bruce's Mark
• 17 Deep South Whittle Reef
• 18 Anvil Rock
• 19 SS Lusitania

Back to the Alphabetical list of sites, or list of reef dive sites in the Southern False Bay offshore reefs area

Other regional dive sites:

• Dive sites of Table Bay and approaches,
• Dive sites of the Cape Peninsula west coast
• Dive sites of the Cape Peninsula east coast
• Dive sites of False Bay east coast
• Fresh water dive sites of the Cape Town Metropolitan Area