Diving the Cape Peninsula and False Bay/Boardroom pinnacle

The dive site Boardroom pinnacle or Outer Justin's Caves is an inshore, rocky reef, with a large swimthrough cave and air trap in the north Oudekraal area on the Cape Peninsula Atlantic Seaboard, near Cape Town in the Western Cape Province of South Africa.

Understand

This site has one of the largest swimthrough caves in the region, with a relatively large air-trap dome. It is near enough to the shore to reach using a diver propulsion vehicle.

Position

Boardroom pinnacle 📍: S33°58.767' E018°21.151' About 620 m directly offshore from the Twelve Apostles hotel. This site is in Table Mountain National Park Marine Protected Area since 2004. A permit is required.

Name

The site was named "The Boardroom" by the divers who first reported it in December 2020, saying that the cave is big enough for a boardroom. The alternative name "Outer Justins Caves" references the nearby and much better known inshore site Justin's Caves, and also the name of one of the discoverers, who is not, however, the same Justin that the inshore caves are named for.

Depth

Maximum depth at the Boardroom pinnacle is about 19 m. and the top of the pinnacle is about 10 m. (Average depth of a dive is likely to be about 18 m.) There are deeper and shallower points in the general vicinity. Maximum depth nearby may exceed 30 m.

Visibility

Visibility is variable in the same way as other sites in the area, The site was found on a day with visibility exceeding 20 m, and first surveyed a couple of weeks later in about 2 to 3 m.

Topography

Granite reef with large corestone boulders, as is common in the area. The Boardroom is a domed swim-through under a huge boulder on a rocky bottom at about 19 m, and is about 33 m long north to south, and about 14 m east to west, with a flattish top about 10 m below the surface. The top of the air space is probably at about 16 to 17 m depth. There is access from at least two places, from the south side, and from the northeast side of the covering boulder. A short distance downslope to the east there is a cluster of large boulders. About 50 m further south another area of small caves and swimthroughs has been reported, but an accurate position is not yet recorded.

Geology: Pre-Cambriam granite of the Peninsula pluton. No large sandy areas have been reported from the vicinity yet.

Conditions

Get in

The site may be done as a boat dive, either from Oceana Power Boat Club slipway in Granger Bay, which is slightly closer, or from Hout Bay. The site was discovered on a shore dive, using scooters, but finding it would require a GPS.

See

Marine life

The top of the reef at about 10 m has a fairly dense forest of Split-fan kelp, which is quite usual for this area.

Other organisms reported from this site include: <gallery mode=packed> File:Invertebrate reef life at Boardroom pinnacle P1040172.jpg|Spponges, corals and sea urchins File:Large barnacle at Boardroom pinnacle P1040221.jpg|Barnacle, seaweeds and encrusting sponges File:Zoanthids at boardroom pinnacle P1040225.jpg|Soft corals </gallery>

Features

There are several swimthroughs, overhangs and deep gullies, some are described in the Topography section. The air trap dome under the boulder is a few metres from the entrances to the overhead zone, and the way out may not be visible from the top of the dome if the visibility is poor, but will usually be visible as a lighter area once one has descended to the base of the covered area. <gallery mode=packed> File:The air trap at Boardroom pinnacle P1040261.jpg|Inside the air trap at Boardroom pinnacle File:The air trap at Boardroom pinnacle P1040263.jpg|Inside the air trap File:The air trap at boardroom pinnacle P1040264.jpg|Inside the air trap </gallery>

Photography

If the visibility and natural lighting are good, wide angle lenses with ambient lighting and possibly fill-in flash will provide some spectacular views, otherwise macro equipment with flash or video light will almost always produce good results. The use of flash for intermediate distances should be reserved for external strobes to minimize backscatter. Even on a good day there will be some suspended material.

Suggested Routes

At this stage only one route is suggested, not because of lack of things to see, but because very few of the features have been mapped.

Drop a shot line and enter at the top of the pinnacle, swim west over the pinnacle and descend to the bottom of the wall. Find the entry to the swimthrough cavern along the bottom edge of the east side and find the air trap dome. Ensure that you can find your way out again. This should not be difficult, as if you descend to the floor, light should be visible from the edges in several places even in poor visibility. After exiting, swim around to the large overhang at the north east corner, then do whatever pleases you until it is time to surface. If you find anything interesting, let us know on the talk page, or add the information yourself.

Stay safe

Hazards

No known site specific hazards other than the risks associated with diving under a restricted overhead, which is optional. Check your gas pressure before entering

Skills

No special skills required. Certification appropriate to the depth is expected, and the ability to deploy a DSMB is recommended

Equipment

Dry suit recommended, as it will normally be cold if the visibility is good. Nitrox can significantly extend safe dive times. A DSMB and Reel are recommended to indicate your position to the boat while surfacing. A light is recommended if you intend to enter the cave.

Nearby

Back to the Alphabetical list of sites, or list of dive sites in the Oudekraal area

Other regional dive sites: