The Cape Town Dive Festival 2012

The Cape Town Dive Festival 2012 website
The Cape Town Dive Festival 2012 website

The very first Cape Town Dive Festival will take place on Friday 10 and Saturday 11 August 2012, at the Cape Boat and Ski Boat Club at Miller’s Point. As many of the dive operators as possible are co-operating in the planning. The aim is to promote diving in Cape Town, and we’re very excited about this event!

The cost is R200 to register, which gets you a T shirt and access to the discounted boat dives, competitions and festivities, and R100 for each boat dive you do. So if you do two boat dives, you’ve already saved yourself some money!

There are six dive boats launching three times a day to seven sites (wrecks and reefs at a range of depths for all qualification levels), as well as frequent shore dives to visit the sevengill cowsharks. There’s something for everyone – from the wrecks of the SAS Fleur, the MFV Orotava, the SAS Pietermaritzburg and the SAS Good Hope to the reefs at Pie Rock, Outer Castle, Partridge Point (for some seals!), Batsata Maze and more.

Visit the Dive Festival website for more information! Clare is handling bookings, so when you book your spot you’ll be interacting with her. If you want to join the Learn to Dive Today rabble on the boat, contact me to find out which dives we’ll be participating in. If you want to rent kit and cylinders on the day, be sure to let me know as soon as possible.

Directions to Harbour Island

Harbour Island
Harbour Island

Harbour Island is where you’ll typically go to launch to dive the eastern side of False Bay by boat. There is a slipway right next to the Gordon’s Bay Boat Angling Club, with perhaps the best-placed Ocean Basket franchise in Cape Town on the opposite side.

The slipway at Harbour Island
The slipway at Harbour Island

There is a residential development in the area too. There are public loos and a freshwater tap near the slipway that is convenient for hair and face washes before and after dives. Here’s Harbour Island on a map:

View Larger Map

I’m not going to type out directions, but you can see that the marina lies on Gordon’s Bay Drive, which is the main drag through Gordon’s Bay. It’s a few minutes’ drive from Indigo Scuba. The old Gordon’s Bay harbour and the Gordon’s Bay Yacht Club, where there is also a slipway, is further around the coast, in an easterly direction (on the far side of Bikini Beach).

Friday poem: Sonnet 135

The poet is grappling with rejection! Want to read a bit more (with the usual Wikipedia caveat)? Click here.

Sonnet 135 – William Shakespeare

Whoever hath her wish, thou hast thy ‘Will,’
And ‘Will’ to boot, and ‘Will’ in overplus;
More than enough am I that vex thee still,
To thy sweet will making addition thus.
Wilt thou, whose will is large and spacious,
Not once vouchsafe to hide my will in thine?
Shall will in others seem right gracious,
And in my will no fair acceptance shine?
The sea all water, yet receives rain still
And in abundance addeth to his store;
So thou, being rich in ‘Will,’ add to thy ‘Will’
One will of mine, to make thy large ‘Will’ more.
Let no unkind, no fair beseechers kill;
Think all but one, and me in that one ‘Will.’

Wind Atlas for South Africa (and divers too)

The Wind Atlas for South Africa (WASA) project was launched in mid-March, having been funded by the Danish government (masters of wind farming), and the United Nations Development Program-Global Environment Facility (UNDP-GEF). The atlas shows wind direction, frequency, and estimated power output, and the data was collected from a grid of wind measurement stations all over the country. Its primary use will be to assist South Africans in tapping the energy of the wind to generate electricity. This is incredibly exciting, as within a few months a wind turbine offsets the carbon emissions required to construct it, and then runs virtually emission-free for up to 20 years. Also, we’re all really tired of Eskom (supplier of electricity) encouraging us to purchase less of its product (electricity), and randomly switching off the power when we’re stuck in a shopping mall parking area or trying to cook dinner. I would love to see an economist’s take on that dogshow.

WInd farm off the coast of Denmark
WInd farm off the coast of Denmark

I digress. There’s quite a bit of techinical information on the CSIR WASA site, as well as in some of the news articles describing the project, but the gist of it is that measurements have been taken over the last 2-3 years, and supplemented by a mathematical model to provide a smooth map of wind speeds across most of South Africa. Thirty years of global data was used to calibrate the model.

All well and good, you say, but how on earth is this relevant to diving? Well, you’ll notice that the Learn to Dive Today newsletter frequently contains reference to wind speed and direction, and this affects where we can dive, and when. In summer, if the southeaster has been blowing, it’s Atlantic or eastern False Bay. In winter, the northwester makes the latter two destinations undiveable, but cleans up western False Bay delightfully. So wind is pretty central in the lives of local scuba divers. Wind is also the primary generating force for waves and the massive swells that arrive at our shores from the Southern Ocean, which affects our diving too.

Wind is also fairly central to the lives of everyone else who lives in this part of the world… If you speak to any Capetonian about the weather (a favourite topic), the wind is bound to come up (in discussion, not literally)!

30 year annual mean wind speed (measured in m/s) 100 metres above ground level
30 year annual mean wind speed (measured in m/s) 100 metres above ground level

With all this in mind, it’s quite gratifying to look at a WASA map, and see that our local obsession is justified. The Cape Peninsula and Gordon’s Bay area are among the windiest in the entire area mapped. Red indicates wind speeds of 10 metres per second, the green is about 5 metres per second, and purple (there’s almost none of it) is virtually windless. The source of this map is here.

If you’re a local diver, I encourage you to pay attention to the wind. Even if the weekend’s not windy (most people’s diving time), the wind in the week before will give clues as to what the sea conditions will be. Reading the newsletters of ethical operators will give you good insight into local weather patterns, courtesy of his years of reading the wind and water. If nothing else, an awareness of the wind will lead you to feel less disappointed when a dive is cancelled because of it, and enable you to make safe diving choices about what sort of conditions you want to go diving in. Unfortunately not all dive charters will hold back on launching when conditions are poor, and you can avoid an expensive zero-viz dive or getting seasick (or lost) on the surface by watching the weather yourself and making deductions.

Newsletter: The same, but different

Hi divers

The last few weeks have been eventful for the marine world in Cape Town. For some thoughts about chumming, which has been very much in the news lately, you can click here and here, and for some general thoughts you can read this blog post. The ocean is a complex and ever-changing place, but it’s the same old ocean that we dived in a month ago. There’s something new to see every day – don’t let political drama and media hype put you off!

False Bay seen from Boyes Drive
False Bay seen from Boyes Drive

Back to diving… or the lack therof

The picture above shows the patchy and murky waters of False Bay. Our diving plans for this entire week have been on hold as the weather, water and wind have not been of a nature typically required for diver training.

Christo and me on the boat with the BOS 400 in the background (picture by Maurice)
Christo and me on the boat with the BOS 400 in the background (picture by Maurice)

We did venture out last Saturday and dived the BOS 400 in very misty conditions. The visibility was around 15 metres but there was a huge fog bank hanging about so we decide to skip a second dive. I had cancelled shore dives for the weekend but believe it was a bad call as reports of great visibility and flat seas served to remind me that weather forecasting is best left to the experts.

We took the boat out today and dived with the cowsharks at Shark Alley and the seals at Partridge Point. The conditions were more windy and choppy than the weather forecast predicted, but the visibility was an acceptable 6 metres at Shark Alley and about the same at the seals, but very surgy.

On the boat in Maori Bay (photo by Maurice)
On the boat in Maori Bay (photo by Maurice)

Weekend plans


We will launch from Miller’s Point and do a double tank dive or just one dive (I’m not taking the boat out of the water in between dives, so you can’t do just the second dive), maximum five people, dive site(s) and depth dependent on who books and how many dives you want to do.

Saturday and Sunday

Shore dives for training and Discover Scuba Diving.

Monday and Tuesday

Back on the boat for a double tank or a single dive (weather permitting) – sites on at least one of those days to be suitable for Open Water divers.

If you would like to dive, please let me know your preference for what day, and if there’s a particular site (False Bay side) that you’d like to visit. No promises, but your input is important!

Cape Town Dive Festival

This is going to be a big event, to be part of it you need to go to and register and book your dives. I cannot book for you, but you can do the dives I have booked if you wish. Or if you are tired of seeing my fins, pick any of the options available providing they are within your qualification.


Booked and paid for and we leave on Monday 7 May returning on Saturday 12th. So no diving with me that week, here, but you can still join if you’re tired of the office.


Tony Lindeque
076 817 1099

Diving is addictive!

Diving with an alpha flag

The vast majority of new divers in Cape Town know where Long Beach in Simon’s Town is. Irrespective of the dive school you choose for Open Water training it is in most cases quite likely you will do at least one dive at Long Beach. There is a very good reason for this: it is diveable in most conditions as is usually the last place on the coastline to be blown out. It is a safe environment and a perfect place for training as it is by far one of the easiest shore entries around.

Divers enter the water as a rubberduck speeds past
Divers enter the water as a rubberduck speeds past

Although it is known to all dive trainers as a training site, very few visitors know this and not all water users (boaters, kayakers and paddle-skiers) are aware of your presence in the water. The average boater does not know the tell-tale signs of bubbles divers make, and why should he? But being struck by a paddle-ski, a propeller, or the keel of a sailboat is going to hurt you and it could easily kill you.

It is not too often that boats buzz by the beach, but on occasion the Navy boats as well as paddlers, and fishermen drive by as well as visitors to the coast with their recreational boats. Even the NSRI uses this beach for training of their boat crews on occasion. Part of a skipper’s training is to be aware of things floating on the surface: buoys could indicate nets, for example, that would snag the propeller, and thus boaters are trained to avoid or approach carefully any such flotation device.

There is no evidence of a surface marker buoy
There is no evidence of a surface marker buoy

So why do most divers dive without any form of warning to a boat that they are there, and why would they do so when part of what they are teaching new divers involves ascending in random spots all over the area? “We seldom ascend during a dive” is most often the answer as to why yet there are several surface skills, training ascents and the constant risk of an unplanned ascent by a new diver coming to terms with buoyancy (or in some cases having a mild panic attack and dashing to the surface).

The simple answer is that it is not required by law in South Africa to tow a buoy or alpha flag… But then it’s not law that as an Open Water diver you can’t go to 50 metres during a dive. You are taught not to exceed your training level, your logic will also most likely tell you it’s a risky plan, but if you are foolish enough to try who would stop you?

More divers entering the water without a buoy or flag
More divers entering the water without a buoy or flag

It is fortunate that the dive industry is largely self-regulated and as divers we are free to explore the ocean at will. Scuba diving is a very safe sport and provided you stay within the guidelines of you training agency you will have thousands of safe and enjoyable dives. When doing a boat dive, the skipper will typically erect an Alpha flag to indicate to other boats that he has divers in the water (if your skipper doesn’t do this, it’s time to switch dive charters to one that’s more safety conscious).

You could dive without a pressure gauge – but that would be foolish – you could dive without a mask, but then you would see very little, and you could also dive without an alpha flag, but none of the surface water users would see you or know you were there. Would that not be foolish?

Effects of chumming in False Bay

Following on from my post on Saturday regarding the scientific studies done on the effects of chumming elsewhere in the world, a study done in False Bay in 2004 has been brought to my attention by the team at Shark Spotters (thank you!). Much more should be made of this work!

Effects of provisioning ecotourism activity on the behaviour of white sharks Carcharodon carchariasLaRoche, Kock et al (Marine Ecology Progress Series, May 2007)

This paper (summary here, full text here) describes a study done in June-October 2004, using acoustic tags and receivers on the sharks and sea floor around Seal Island. Over the five month period, the researchers were at sea for an average of 15 days per month, ten hours per day. Despite this their sample was too limited to draw conclusions about certain things – this is an excellent demonstration of how hard it is to do science in an ecosystem.

The findings are similar to those of the Australian study I mentioned on Saturday in that it was observed that the chum had an effect on shark behaviour, but that it was fairly minimal. The authors estimate that 10-20 sharks are present around Seal Island at any one time during the winter (May – September), but only a small fraction of these approach to investigate the material placed in the water to attract them to the boats.

Moreover, the sharks’ response to the presence of chum decreases with time – during the first hour that a shark was recorded on one of the acoustic receivers, the chumming appeared to have a significant effect on its location at the island. In subsequent hours, however, the sharks seemed to lose interest and resume ordinary behaviour. This effect was also observed on a larger time scale, with decreasing interest over a number of days.

No effect was observed on their predation rate (how many seals they caught) suggesting that (even when they got hold of the bait being used) the chum didn’t cause the sharks to substitute their usual diet with the bait or with some other source. Sharks were seen at the boat only 36% of the time that they were actually at the island. Sharks did swim closer to the surface when the researchers were chumming in the area, but resumed their normal swimming depth elsewhere around the island.

These results are the exact opposite to what one would expect if the sharks were becoming conditioned by the presence of tourist boats chumming at Seal Island. Conditioning refers to changing behaviour by means of some sort of stimulus, in this case by rewarding the shark with a smell or taste of chum (the stimulus) each time it approaches a tourist boat, and thus causing it to approach all boats (for example – the response). If sharks were becoming conditioned by the chumming, one would expect the time they spend around the boat to increase over time, and that they might even approach boats that were not placing any attractant in the water.

There is still work to be done, however:

Unfortunately, conditioning is not the only way that chumming can directly affect the sharks. Extra provisioning could potentially alter residency times at the island, in either a positive or negative direction. It could also theoretically affect shark population structure around the island, if dominant and subordinate individuals react to the chum in different ways. However, despite the fact that it would seem reasonable to surmise that the patterns observed in our data would not translate into changes in shark residency times at the island, nor could the impacts of sparse provisioning have substantial effects on population structure, the short-term nature of the present study makes it impossible to draw any inferences regarding these topics.

I’d suggest you read the original paper if this kind of thing interests you. Even if the statistical jargon (Komolgorov-Smirnov tests, t-tests and the like!) is mysterious to you, it’ll give you a good idea of how arduous it is to conduct a study of this nature (750 hours at sea, in winter, anyone?), how frustrating it can be (the presence of cage diving operators at times meant that their observations had to be discarded in the interests of statistical rigor), and what goes into analysing the data. There is no real place for “gut feel” – it can lead your enquiries in a particular direction, but the final analysis is a statistical, evidence-based one.

Lessons to learn

The events of the last few weeks are still very fresh and raw, and I am sure that there will be many more statements, comments, theories, opinions and findings following the public relations debacle of the Ocearch research expedition in False Bay (and other locations along the South African coast) during the month of April, and the terrible loss of a local bodyboarder to a shark, on the eastern side of False Bay on Thursday.

I have been planning to write this for several weeks, and thinking about the the points I wanted to make, I think they’re even more pertinent now. So here’s my list of things I think that we can take note of, or remember, from the last few weeks of media back and forth surrounding the Shark Men research in False Bay:

Capetonians have strong feelings about “our” sharks. Some of us are protective of them and are suspicious of interference with the population around our coast, which explains the outcry when it was revealed (through various roundabout, accidental channels) that the former cast of the National Geographic Shark Men show was coming to Cape Town to hook, exhaust, remove from the water, sample, tag, release, and – it was thought, based on their track record elsewhere – potentially harm some of the white sharks that frequent Seal Island.

Opposition to the Shark Men project came from others, too, such as surfers, who are generally fearful of the sharks, and have concerns and opinions around the use of chum (I wrote about this yesterday) to attract sharks to boats for ecotourism and research purposes. Whether these feelings and opinions are based in fact or not, they are heartfelt and it is disrespectful to ignore them or dismiss them without an informed discussion.

There is not enough trust that the government will do what is in the best interests of both sharks and water users. This is born partly (and perhaps slightly unfairly since several different departments are involved) from a long list of high profile marine-related bunglings – the latest being:

The City of Cape Town, on the other hand, has shown itself to be even-handed, fair, rational and willing to listen to scientific opinion when managing its facilities and resources. Here’s the City’s assessment of Thursday’s incident at Kogel Bay. It’s a breath of fresh air, I think!

In almost all cases, too much information is better than too little. This follows on from the previous point. The history of official communication regarding activities in the multi-use area of False Bay is quite dismal:

  • the experimental whelk farming was kept under wraps – despite several locals raising questions about the nets being put up in Fish Hoek bay – until a shark died in the nets;
  • a local environmental reporter discovered and broke the story that the City of Cape Town was planning to implement an exclusion net (different from the gill nets off Durban that are designed to kill sharks, dolphins, whales, turtles, rays and anything else that swims into them) around a designated swimming area at Fish Hoek beach, thus forcing the City to release a statement regarding the net; and
  • the Department of Environmental Affairs was less than forthcoming regarding the Ocearch permit, and have spent much of the time on the back foot responding to allegations rather than volunteering information. The only official statement on the DEA website regarding the project is a response to a “shark alert” put out by a member of the public.

In the case of the Ocearch project, I believe there would have been far less alarm and far fewer conspiracy theories had we known from the outset that some of our most respected shark scientists were involved and would be supervising the tagging activities. If the authorities are unable to cite any convincing research findings regarding the effects of chumming (although there have been several international studies, Dr Boyd was unable to recall any on CapeTalk on 13 April), then perhaps it would have been prudent to lay the available facts before water users regarding the forthcoming activities in the bay, and allow them to make decisions based on their personal tolerance for risk.

One might argue that speaking too much about sharks from public platforms creates fear in people’s minds and brings them too much to the fore of beach and water users’ consciousness, but in my experience the general public will talk and think about sharks anyway. They are a reality of living on the fringes of False Bay, and even when there is no shark-related news, they are still in people’s minds. Providing facts gives the public a firm baseline from to discuss sharks, and being able to discuss issues of shark conservation, the risks to water users, and the effects of chumming with hard science to back it up will elevate the quality of dialogue among surfers, divers, beach users and all those Capetonians who think about sharks now and then.

As I said yesterday, we will never put the shark bites and chumming question to rest until we do some hard science to figure it out. That means tagging sharks – lots of them – in False Bay, with tags that allow us to monitor their behaviour both in the short (critical) and long term. Who will fund this research? It takes millions of rands to do something like this properly. The Ocearch project may have gone some way to answering this question, but we will now probably never know how far.

The science needs to be done carefully, for all the reasons I outline above. I thought the Save Our Seas statements regarding the recent research and subsequent incidents showed an extraordinary sensitivity to the complexity of the issues at hand. You can read the entire statement here, but in conclusion here’s an excerpt:

Any activity with white sharks in the waters off of Cape Town should respect the delicate balance between humans and sharks. The best thing for shark conservation is safe beaches and bathers and it is important to work in these shared spaces with great care.


A study has been done on the effects of chumming in False Bay – click here to read about it!

We need to talk about chumming

On Thursday a young man in his youthful prime was bitten by a shark in False Bay, and lost his life. Coincidentally, in addition to the usual (limited – three operators only) cage diving activities at Seal Island, an American research vessel had been operating in the bay in the days prior to the attack, using chum to draw sharks closer to the vessel in order to tag them. Naturally, many members of the public – who until last week had been given very little information aside from rumours and gossip on the subject of this highly-funded research cruise – are pointing fingers at the practice of chumming, claiming that it has to be changing the sharks’ behaviour and leading to increased risk to water users in False Bay.

Actual scientific research on the subject

I have read two papers on the subject of chumming (Australians call it berleying) and its effect on shark behaviour, as well as a brief discussion in Thomas Peschak’s excellent book South Africa’s Great White Shark.

The effects of berleying on the distribution and behaviour of white sharks, Carcharodon carcharias, at the Neptune Islands, South AustraliaBruce & Bradford (CSIRO study)

This paper is based on studies in Australian waters on white sharks (summarised here, full paper here), at a seal colony (North Neptune Island in South Australia, 60-70 miles offshore) where shark ecotourism takes place. Over the years the number of days on which the water is chummed, and the number of operators doing so, has increased, and a previous study done in 2001-2003 provided a useful baseline from which to work. A study comparing the movements of sharks tagged in 2010 with sharks tagged in 2001 found that, while no sharks took up residency at North Neptune Island (white sharks are generally highly migratory and only spend short periods in one place), the average amount of time that sharks spend at the island has almost doubled (to 21 days) over the last 10 years.

The study also found that the daily average number of sharks seen by the operators has increased, but rather than indicating increased shark numbers, this reflects the fact that sharks are staying longer at the island. The sharks’ movements around the island also more closely match those of the cage diving operators, as they arrive and depart at around the same time as the boats do each day (regardless of whether there are operators present).

It’s important to note that the Neptune Islands are far offshore, and not much else seems to happen there except for shark viewing.

Don’t bite the hand that feeds: assessing ecological impacts of provisioning ecotourism on an apex marine predatorHammerschlag, Gallagher, Wester et al (Functional Ecology, March 2012)

The second paper (summary here, full text here) studied two separate populations of tiger sharks, one in Florida, where chumming is banned, and another in the Bahamas where there is a thriving shark diving industry that feeds the sharks to draw them closer to divers. The hypothesis was that if the Bahamas sharks were responding to being fed, their distribution and movements would concentrate far more closely around the feeding areas than the Florida population does around its local area.

The conclusions were surprising: not only did the Bahama sharks range freely, but they did so over distances five times greater than their Florida cousins do, suggesting that they are not affected in a measurable way by being fed on baited shark dives.

A note about methodology

You will notice that both these studies had a sort of a “control group” that was unaffected (or less affected) by the factor (chumming) that they wanted to study. In the Australian one, the authors were able to refer back to a previous study done when there were fewer cage diving operators going out for fewer days a year, to see what had changed, knowing that one environmental variable (frequency and amount of chum) had increased. In the American study, two separate populations of sharks could be studied.

This is good science – in complex systems you cannot draw conclusions without attempting to eliminate the other factors which could influence your observations. While it would have been interesting in and of itself to find out how far the tiger sharks of the Bahamas range, the information would not have enabled any conclusions to be drawn about factors specific to that population (being chummed) without the inclusion of a parallel study on the Florida tiger sharks.

The False Bay chumming question

I’m a mathematician. It’s easy to study numbers and equations: they sit still on the page, they don’t interact with other equations unless I make them do so, and the results of my calculations are (hopefully) unambiguous. It’s this purity and dichotomy between truth and falsehood that atttracted me to the subject in the first place. Studying the natural world seems much harder to me. Sure, you can study sharks, but there are a thousand other variables – many that are specific to the location of the shark population in question – that can affect your study.

Thinking locally, seal populations might rise and fall because of external factors or changes in their food source (or, if you’re Namibian or Canadian, culling). Climate change, ocean warming, or fishing pressure (or something else) might adjust the abundance and type of fish that visit False Bay and how long they do so, thus changing sharks’ movements around Seal Island and inshore. Teasing out the effect of a single activity – chumming, in this case – is far from straightforward. It takes time, and lots and lots of money.

We will never, ever put this question to rest until we can do the science, run the numbers, draw the maps, and get enough observations to draw statistically relevant conclusions. The movements of the sharks both within False Bay and in the open ocean needs to be studied. We can make inferences about the effects of chum in False Bay from the research done in other places (such as the two papers I mention above), but the uniqueness of every location, the pressures exerted on it by the populations along the coastlines nearby, and its own peculiar history means that – in this situation, at least – I don’t think we can stand on the shoulders of others in order to draw hard and fast conclusions.

The sooner we start, the better – in the (probable) absence of an earlier local study such as the one used in the Australian research paper, some clever science will be required to get meaningful results. It’s a great pity and a terrible irony that the very research that could have led us to some answers about the effects of chumming has been suspended – because (it seems) of suspected or perceived culpability in the shark bite incident on Thursday. And no one is in a position to say whether the activities of the research cruise did lead to the incident, because we have no prior research from which to draw conclusions. Thinking about this too much is depressing, and gives me a headache. More tomorrow.


Tony has been on baited shark dives in the open ocean and at Aliwal Shoal, and we both have been shark cage diving in Gansbaai. We found it a life-altering experience to be with the sharks in these settings, knowing that without the use of chum the chance of seeing any sharks would have been vanishingly small. We are both in two minds, and have been for a long time, as to whether using artificial means to draw the sharks to a boat outweighs the wonder of seeing them in the water, and the effect this can have on one’s view of sharks as something to be protected rather than feared. Perhaps our having been on baited shark dives shows that we feel that the ecotourism and mindset-altering benefits of these dives is more significant than the possible additional risk of changing the sharks’ behaviour with chum… I don’t know, and I can assure you the debate occurs at least once a week in the Lindeque household!


A study has been done on the effects of chumming in False Bay – click here to read about it!