False Bay offshore: granite pinnacles, Whittle Rock and the long ride out

Most people who dive Cape Town dive the coastline. Kelp, granite, a short boat ride, back for coffee. The offshore reefs of False Bay are a different thing entirely: pinnacles standing alone in open water, reachable only by boat, and dived only when the sea lets you.

That is exactly why they are worth the trip. These reefs sit far from the launch sites and far from the murk that hangs along the shore, and the visibility out there can be very good, sometimes better than anywhere inshore on the same day.

The catch is that it is not reliably predictable. You go when the weather gives you a window, which is not often. Locals who chase those windows say it happens more often than people used to think.

A region with more sites than you can dive

The wider Cape Peninsula and False Bay region holds over 300 named dive sites with recorded positions, all within a day trip by road from anywhere in greater Cape Town. The offshore group is one slice of that. The Wikivoyage guide covers each site in its own sub-article, with maps where they exist.

Those maps are worth a word. SURGMAP charts are made by swimming the contours towing a GPS buoy, usually accurate to within a couple of metres, reliable for what they show but seldom complete. Wreckless Marine uses multibeam sonar, generally accurate to within a metre. Tall pinnacles may still be out there unrecorded.

The reefs, area by area

Geology sets the character. Seal Island, Whittle Rock, Anvil Rock and Bellows Rock are granite, probably all part of the Cape Peninsula pluton, weathered into corestone shapes: rounded boulders, clefts, swim-throughs. Steenbras Reef, East Shoal and York Shoal are hard sedimentary rock, and Rocky Bank is sandstone. On the sedimentary reefs the dip of the strata does most of the work.

Seal Island in the northwest is the odd one out. It is cage diving, done through a licensed shark cage diving charter, and the cages sit about 2 m down. You go for one reason: sharks. Other fish come to the bait, but that is not the point.

York Shoal lies just south of the island, hard sedimentary rock running from 4 m to about 28 m.

Between the wreck of the Fleur and Simon's Town sit the Blue Flame Pinnacles, 25 to 33 m. The north group is a large granite reef with long ridge-pinnacles running roughly northwest to southeast. The south group is a tight cluster of very steep corestone pinnacles rising from a low outcrop that barely clears the sand.

Whittle Rock

If you dive one offshore site in False Bay, it is this one. Whittle Rock is a large spread of granite corestone reef east of Miller's Point, surrounded by sand. The top of the shallowest pinnacle is at about 4 m, the surrounding sand mostly 30 to 40 m, and parts of the reef system reach about 42 m.

It is big enough that the topography changes as you move across it, which is why the guide breaks it into named features. The main pinnacle, the boulder that is actually called Whittle Rock, stands on top of the main outcrop with a gully to the east and a second pinnacle a few metres southwest.

A few features people talk about:

• West Pinnacle: a huge boulder wedged into the top of a gully, forming a big swim-through
• Northeastern Pinnacle and Euphrates Gully: three large wrought-iron anchors on the sand, thought to be from the English East Indiaman Euphrates
• Shards Cluster: huge angular boulders at the northeastern edge, projecting out into the sand
• Bruce's Reef, also known as Stingray Central, a raised area of reef inside the MPA
• Cathedral Pinnacle, a large boulder at the end of a ridge above a sandy strip at 18 m
• Criss-cross Cracks: a flat-topped area split by narrow, moderately deep cracks

Around the main reef are the Off-Whittle western, eastern and southern reefs. Some of the eastern and southern sites have been dived and recorded. The western ones, lower in profile and deeper on average, have no reported dives at all.

Weather, water and when to go

There is less seasonal pattern here than you might expect. Summer south-easters have enough fetch to build unpleasant sea states, and in winter the north-wester does much the same. The area is exposed to south-westerly swell, though that energy crosses a wide continental shelf, much of it under 100 m deep, and loses a lot on the way.

Temperature depends on depth and season. In summer you can find 20°C at the surface and 9°C at 28 m, sometimes with a distinct thermocline, though usually the change is smaller. In winter it may be close to constant top to bottom. Thermoclines tend to show up from midsummer into autumn, often alongside poor surface visibility with clearer water below.

The modelled averages show what the numbers look like across the year: warmest water around February to April, coolest in July, and wave heights that never really settle. Averages smooth out the good days, though, and the good days are what these reefs are dived on.

Planning it

Everything out here is a boat dive, and the trips are long and often bumpy because the sites are exposed from all directions. Charters run from the peninsula, and Cape Town puts every one of these reefs within a day trip by road. Parts of Whittle Rock lie inside the MPA, and the guide notes which features fall in and out.

Keep your plans loose. Offshore False Bay rewards divers who can move a booking when the wind swings.

When you finally get your window, log it in Scubaspot: the depth you hit on the sand around Whittle Rock, a photo of the boulder wedged over the West Pinnacle swim-through, and a note on whether the Euphrates anchors were visible. Rate the site so the next diver watching the forecast knows what the ride out is worth. Start at scubaspot.co.