Posted by: Clare | 22 December 2011

The Learn to Dive Today blog is moving!

Hello readers! Exciting news – the location of our blog is moving. We’ve developed beyond the (wonderful) shared hosting environment of and have recently set up a (self-hosted) blog account. You can find it here:

Our email subscribers should not notice a change – you’re all still subscribed to the blog and will continue receiving the posts by email without a break. Our followers will have to either sign up for email posts, or just bookmark the new blog for when you want to check it out. All the old posts are still there.

Visits to will start seamlessly redirecting to the new blog address, quite soon!

Posted by: Clare | 21 December 2011

Suunto D6 dive computer

I’ve been using the Suunto D6 dive computer for about eight months now, having finally got my grubby paws on it just after returning from our last trip to Sodwana. I think it’s about time I write a little review of it, because Suunto have just released the D6i and before you know it my computer will be a museum relic.

Specifications and appearance

The D6 is near the upper end of the range of Suunto dive computers – the model I have will now set you back in the region of R10,000 and there are several cheaper but no less effective offerings. The USB interface cable that will enable your dive computer to talk to your computer will set you back up to a further R1,500 – although this item is frequently advertised on special by Suunto stockists and occasionally as a special bundled with the dive computer, so keep your eyes open. It’s far more usual, however, to have to buy this innocuous-looking cable separately, and gasp at the price.

You can choose an elastomer strap or a metal strap (for about R2,000 more). Although the metal strap looks really cool, it’s not really practical if you dive in varying water temperatures and change the amount of neoprene on your wrist frequently. The computer functions as a dress watch if you want to use it as one – it displays the time constantly when not in dive or memory mode – but it weighs more than a slab of chocolate (130g) and is far too large for the average lady’s wrist, so I don’t use it for this purpose except when travelling (to deny the baggage handlers at OR Tambo Airport the privilege of stealing it).

The computer has a four button interface that I find very intuitive, and I could figure it out to a large degree without reading the manual. That said, if you buy a dive computer, YOU MUST READ THE MANUAL! Don’t be a fool – you want to know EXACTLY why the thing is beeping at you, what it looks like when you go into deco, and be very sure (as one clown – who was buddied with us once because he didn’t know anyone on the boat – wasn’t) whether the “3” you see on the screen indicates a time in minutes, your current depth, or the number of brain cells you have. Read the manual!

Air integration and the D6i

The D6 has actually been replaced by the D6i, which is functionally identical but has more internal memory, and is capable of air integration with an optional (heart-stoppingly expensive) dongle that you attach to your cylinder and reads remaining air. The computer will then give you an estimate of remaing dive time based on air consumption to date. I have no interest in this (at the time I bought the D6, air integration was the main distinguishing feature from the D9) – I’d use a pressure gauge regardless, and wouldn’t feel comfortable trusting what I see as an physical, analogue process (displaying the air remaining in my cylinder) to a potentially failure-prone piece of electronics.

I know I may sound like a luddite here, but an experience Tony had on the boat a few months ago confirmed my reservations. Another instructor’s student had an air integrated computer and no pressure gauge (why bother with redundancy?). The air integration with the computer wouldn’t work, but they only discovered this on the boat when they were parked over the dive site, and – after toying with the idea of cancelling the dive, and then swapping kit so the instructor, who should have an excellent feel for his air consumption, had the set up with no pressure gauge – did a very short dive. As a mathematician I can see that having snapshots of your remaining air at 20 second intervals to look at in the dive manager software might be appealing though…

Decompression algorithm

The D6 uses the Suunto Deep Stop RGBM (Reduced Gradient Bubble Model), and allows for continuous decompression as you ascend (instead of forcing you to do stops at particular depths). It also allows you to complete your safety stops at depth – something I haven’t experimented with much, but will be using next time we dive the Lusitania. The computer recommends a safety stop once you exceed 10 metres on a dive, and if you violate the recommended ascent rate it will advise a mandatory safety stop between 3 and 6 metres. I tried to photograph the D6 during a dive where I’d switched on deep stops, but there was a 20 metre layer of green plankton blocking out the light from above, and my flash kept reflecting off the screen protector. Hence the dubious results you see here. I have 28 minutes of no-decompression time remaining, dive time is 11 minutes, depth is 20.9 metres, and my first deep stop will be at 13 metres. Maximum depth (bottom left) so far has been 23.8 metres.

Suunto D6 during a dive - first deep stop is due at 13 metres

Suunto D6 during a dive - first deep stop is due at 13 metres

You’re most likely aware of this, but a dive computer does not measure anything that is going on in your body with respect to dissolved gases. Dive computers use mathematical models – based on the original dive tables, only more sophisticated – that approximate, for the average person, how much nitrogen has gone into solution in the body’s tissues, and how fast it is being released, based on your dive profile. They measure depth temperature, and time, that’s all. For this reason many dive computers, including the D6, have an option for you to set a more conservative calculation algorithm if you’re at higher risk of DCS – for reasons of increased age, high body fat percentage, or any of the other DCS-predisposing risk factors. You can also adjust the partial pressure settings up and down if you so desire, but anything higher than 1.4 bar (ata) strikes me as reckless.

Nitrox and no-fly time

It goes without saying that the D6 is Nitrox capable, and it’s very straightforward to set the Nitrox mix. After one dive on Nitrox, the option to do a repetitive air dive disappears, and you have to manually set the oxygen percentage of your mix back down to 21%. I think this is to force you to think about what gas is in your cylinder. The D6 also handles switching to a richer mix for decompression, and this optional second mix may be set through the same menu system as the primary nitrox mix.

The D6, again like most dive computers, gives a no-fly time after you’re done with diving for the day. This time is usually well under 18 hours, but you’d do well to follow DAN guidelines for flying after diving (usually 18 hours after your last dive) and not bank on the reading given by your computer. Do not be like Gerard, who shall remain nameless, and mistake the time display on your computer for the no-fly time. After a dive on the Aster that ended at about 3.30pm, he announced that his no-fly time was “fifteen hours and twenty nine minutes.” A few minutes later, to his puzzlement, it was “fifteen hours and thirty four minutes!”

Dive Manager software

The Suunto dive manager software, that allows you to examine the details of your dives on your computer screen at home, is not compatible with Apple Macs, so I had to find another solution. I’ll review the software I do use, MacDive, in a separate post. Apparently from “fall 2011”, whenever that rolls (rolled) around, the Suunto software – DM4 – will also be compatible with Apple computers. I’ll test it when I get a chance, and let you know what it’s like… As is apparently wildly popular these days, one can also share one’s sporting activities on the Suunto Movescount site via an automatic link-up from within the software interface. And, no doubt, publish them to facebook.

Electronic compass

Suunto D6 with elastomer strap (right) and titanium strap (left)

Suunto D6 with elastomer strap (right) and titanium strap (left)

One of the major appeals for me of the D6 – and I think the feature that bumps its price up so much higher than the D4 – was the integrated electronic compass, which can be accessed at (almost) any time by holding down the top left (Select) button. In the picture at right, the D6 with the elastomer strap is on the compass display (the one on the right is in the memory log display mode which can’t be accessed during a dive). If you’re not on a dive when you use the compass, obviously the depth and dive time won’t show.

The D6i has updated the compass to allow accurate readings when your wrist is tilted; the old D6 (the one I have) is not as tolerant and you’ll need to keep your arm level as with a standard dive compass. Unfortunately the D6 doesn’t record the compass heading along with the temperature, depth and other dive statistics during the dive – or, if it does, the download software I use doesn’t access it. I suspect the former is true, since I installed Suunto’s own dive manager software on Tony’s PC to check, and there was no sign of compass headings. Boo.

What’s in the box

In the box was the computer, a spare strap, the instruction manual, a disc with the Windows-compatible dive manager software on it, and two or three scratch guards which are trimmed to fit the D6’s screen. I’ve done close to 70 dives with my D6 so far, and the scratch guard is scratched and still doing its job well. Tony’s computer, the Mares Nemo Wide, is protected with some cheap cellphone screen protectors we got from Look ‘n Listen. You can buy a generic size, and then trim it down to fit your phone (or dive computer, as the case may be). We didn’t expect this makeshift scratch guard – which is NOT designed for regular immersion in salt water – to last beyond five or ten dives, but over 100 dives and it’s going strong. I think I paid R60 for the pack of screen protector stickers, and we’ll get nine Nemo Wide-sized ones out of the package.

Buying it

Continuing with the subject of good value, one more tip for the bargain hunters. I actually bought my D6 from Cape Union Mart. They stock Suunto sports watches, and were able to order me a D6 from Suunto in Finland. I had to wait six weeks for it to arrive, and it cost R8,700. What made the deal very sweet was that by buying it on my Discovery Card which gives me a 20% discount at Cape Union Mart (thanks to my years in the Vitality program and points status), the computer ended up costing just under R7,000. I paid a further R1,200 for the download cable (I got that at a dive centre). If you have a few weeks before you need the computer, or are prepared to wait in exchange for some savings, it’s worth getting a quote from Cape Union Mart as to what they’ll charge you. If you’ve got a Discovery Card it’s a no-brainer. Email them via the website for a quotation, and they’ll tell you to print that and take it to your nearest Cape Union Mart to place the order. I had to pay a 50% deposit.

Maintaining it

Finally – if you have a dive computer and live in Cape Town, take it to Orca in Claremont to get the battery changed when necessary, and ask for Chris the “worship manager” (that’s autocorrect gone wild on “workshop manager”) to do it for you. Tony’s students have had baaaaad experiences (a hair across the seal, anyone?!) at other locations. There’s usually not much you can do if the service centre doesn’t seal the computer properly and it floods – your only recourse will possibly be to your insurance company.

Posted by: Clare | 20 December 2011

New gloves (again)!

It seems like yesterday that I was proudly waving about a new pair of blue Seac Sub gloves. Something like 120 dives later, and they’re in quite bad shape… Some of the fingers have punched through, and the seams along the side of my wrist split recently. Boat diving off a rubber duck, towing a reel and camera work are quite hard on gloves, and there’s quite a high attrition rate in the Lindeque household.

Seac Sub 3.5mm gloves with velcro wrist strap

Seac Sub 3.5mm gloves with velcro wrist strap

Enter the new pair of Seac Sub gloves that Andre supplied me with in the middle of November. They’re 3.5 millimetres thick and seal at the wrist with a velcro strap. The seams around the two middle fingers ensure that flexing and dextrous work is comfortable (as comfortable as it can be in thick gloves!). I’ve tested them in the Atlantic and so far so good. I am rather fond of the Seac Sub brand, and my BCD is also theirs.

The old blue pair have been glued, and now live in the “glove box” for students to borrow.

Posted by: Clare | 19 December 2011

Bookshelf: The Living Shores of Southern Africa

The Living Shores of Southern Africa – George & Margo Branch

The Living Shores of Southern Africa

The Living Shores of Southern Africa

It took me a while to get my hands on a copy of this classic volume by Margo and George Branch, with photography by Anthony Bannister. It was a staple in the classroom of every biology teacher I ever had, and occupies pride of place behind the microscope display at the Two Oceans Aquarium, where it has helped countless nonplussed volunteers answer sticky questions about jellyfish reproduction or the eating habits of limpets. It was first published in 1983 and is long out of print.

The first half of the book deals with habitats – the rocky shore, beaches, estuaries, the open ocean, coral reefs, and kelp forests. The authors manage to sneak in quite a lot of physical oceanography without one noticing, as it obviously impacts the flora and fauna that can colonise a particular area. Prof Branch has a special interest in limpets, and I was amazed to discover the intricate adaptations that these unassuming little creatures have to life in the highly competitive, high stress intertidal zone. The section on kelp forests was also wonderful to me, as a regular diver in these parts! I found the chapter on estuaries somewhat dispiriting, given that it was written thirty years ago and it seems unlikely that matters have changed since then. Prof Branch used the Richard’s Bay estuary of the Mhlathuze River as an example of how human interference turned a thriving, sensitive ecosystem into a muddy wasteland in a matter of a couple of years. I have not visited Richard’s Bay, and indeed had not heard anything about this particular estuary before encountering it in this book, so I will have to do some research to find out whether it’s still in such a parlous state.

I found the sections on sharks, seals and whales – under the chapter on man and the sea – puzzling and upsetting, but perhaps they are just a reflection on where scientific understanding of ecosystems was in the early 1980s. I would be interested to hear Prof Branch’s views on these three types of animal today.


On sharks, the authors mention that the Natal Anti-Shark Measures Board (now renamed to something less obviously brutal, but still with the same ultimate aim of killing sharks) killed 11,700 large sharks in eleven years (presumably the decade to 1980). The authors state that it is not known what the effect of removing so many top predators will be on the ecosystem, but do note that there were an estimated extra 2.8 million dusky sharks – a smaller species that has thrived in the absence of tiger and bull sharks – at the end of the eleven year period in question. I was immediately reminded of the fairly recent shark bite that occurred on a baited dive on Aliwal Shoal a few months ago. The culprit was a dusky shark.

What I found unsettling was that very little concern was expressed about the impact of killing so many sharks – highly migratory creatures, in many cases – along a small region of the coastline. The authors do mention the case of Tasmania, which after a few years of shark nets experienced a population explosion of octopus (traditional shark food), who destroyed the local rock lobster population and the profitable local lobster fishing industry. I know that the authors’ focus has been more on coastal species, but their apparent lack of recognition of the role of sharks in a healthy ocean was strange to me given their obvious awareness of how vital is every link of the food web on the rocky shore (urchins, abalone, kelp, sea otters, rock lobster, etc.).


The authors describe the economic value of the seal cull (which in the 1980s was a grim reality of South African life, and in Namibia still is the case). Baby seals were (are) valued for their soft pelts and the oil in their bodies, and mature seals just for the oil – their pelts were deemed to be too battle-scarred to make into a fur coat. The method of killing baby seals with a blow to their heads was sanctioned as humane by the NSPCA because their little skulls are still soft when they are young (and, in a happy coincidence, it doesn’t damage the pelts).

Apart from the economic rationale for killing seals, the authors state that seal colonies “attract sharks” – as if this is a reason to destroy them. I found this extremely confusing – why is one creature more important or desirable than another? The fact that fish, limpets, seals and sharks exist in the ocean means that they all have a role to play, and that somehow these populations lived in balance before human intervention.

Another reason provided for the annual seal cull (which at one point left 35 seals on Seal Island, in contrast to the current population of over 75,000 seals) was that their numbers were increasing “unchecked” and threatening the nesting sites of seabirds on the island. Nowhere do the authors acknowledge that the reason for the seal population explosion could be that their natural predator, the white shark, was fished to the brink of disappearance off the South African coast by testosterone-fueled trophy hunters. Fortunately today shark and seal eco-tourism is big business, and I don’t think (I stand to be corrected) that any seals are legally killed in South Africa any more.


Whaling was an entrenched part of the South African economy from the early 1800s, but was comprehensively banned in 1979, shortly before this book was published. In Blue Water White Death the whaling station in Durban was shown, and whale carcasses were used by the filmmakers to attract sharks. The authors provide a synopsis of the state of whaling in the world’s oceans at the time of writing (depressing – what is the validity of “scientific whaling” when it is conducted by a country that feeds whale meat to school children?) and the population status of various types of whale.

They suggest that, because the small Minke whale competes with blue whales for food, Minke whales should continue to be hunted in order to give blue whales a chance at increasing their numbers. My (admittedly uninformed) view of it is that – what with the population explosion of krill that whaling engendered in the Southern Ocean, the blue whales aren’t even going to notice a few small Minkes dining at the lunch bar with them. Whale populations have been reduced to such a tiny fraction of what they used to be that – for a long time still, everything else being equal – competition for food isn’t going to feature in their population dynamics. My feeling on the matter is that if a Minke whale ever even SEES a blue whale, let alone has the opportunity to argue over a ball of krill with it, it should count itself a lucky little whale and move right along.

The second half of the book deals with specific organisms, their life cycle (beautifully illustrated by Margo Branch), and their habits. The authors focus on invertebrates, as (they say) fishes are extensively dealt with in other volumes. The accompanying photographs were taken by Anthony Bannister, and have not dated at all in terms of quality – they are vivid, clear, and beautiful.

Some of what I learned

I learned a huge amount from this book. It’s clearly provided source material for almost every other South African marine flora and fauna book that has been written, and sentences – that I’ve seen in other books and presentations – kept ringing bells with me (I tend to use my fish ID books quite hard, trying to wring out every last fact from the one-paragraph descriptions accompanying the photos). The authors in fact collaborated on the handy Two Oceans guide, which keeps getting better with each new edition and is indispensible for the travelling South African diver.

  • I learned that the presence of plough shells on a beach generally indicates that it is safe for swimming – these little snails surf in the waves using their large feet as a sail, and if there were rip currents they would be drawn offshore and lost. Their activities on fish Hoek beach are shown to great effect in the BBC’s The Blue Planet series.
  • I loved learning how Rocky Bank protects the western side of False Bay to some extent, slowing down the swells as they enter the bay and causing them to focus their power somewhere near the Steenbras River mouth on the opposite side of the bay.
  • I loved learning about limpets’ “home scars” – the spot on the rock that fits their shell perfectly, and that they somehow return to over and over after foraging for food – and how some species tend little gardens of algae, encouraging its growth by mowing paths in it (and getting fed at the same time). Simple things like the effects of strong or harsh wave action on the slope and sand type of a beach, and as a result the type of life that thrives there, were also fascinating.
  • I learned that 30 years ago (when this book was published) overfishing was already a serious, serious problem.

You can obtain a copy by scouring secondhand book stores,, and

Posted by: Clare | 18 December 2011

Sea life: Starfish at leisure

"Bring me a pina colada by the pool, please!"

"Bring me a pina colada by the pool, please!"

I do not presume – not for one moment – to read the mind of a starfish, but these individuals seem to be living the good life. I think we can all be inspired by their capacity to relax into whatever situation they find themselves in. Most of these specimens were found at A Frame and Long Beach.

Posted by: Clare | 17 December 2011

Bookshelf: Poseidon’s Steed

Poseidon’s Steed – Helen Scales

Poseidon's Steed

Poseidon's Steed

Poseidon’s Steed is marine biologist Helen Scales’ first book; its subject is the seahorse. The book is short – I read it in less than half a day whilst convalescing with a cold – but packed with everything that is interesting about seahorses.

I am well acquainted with the pull that these (mostly) tiny creatures exercise on people – Tony has been obsessed with seeing a seahorse for years, and I was delighted to share in his first sighting during a dive in the Knysna lagoon just after we met. The Knysna (or Cape) seahorse, Hippocampus capensis, features towards the end of Scales’ book, where she discusses the threats to its habitat and its extremely limited geographical range.

The first section of the book situates seahorses in culture, myth and history, and reveals that they have been venerated and depicted in art and design for thousands of years. Scales hops – seemingly – from topic to topic with great ease, and before you realise it she’s painted a complete picture of the seahorse and its role in human life for generations.

Scales describes seahorse biology, clearing up for me the reason why we saw such colour variation among the seahorses we spotted in Knysna: they are able to change their body colour at will. This makes it tricky to differentiate species, but extensive research has placed the current known number of seahorse species at about 40. Unique among animals, the male seahorse actually experiences pregnancy, and these creatures exhibit great fidelity to their mates. Pipefish, those close relatives of the seahorse, are also covered.

Seahorses are popular exhibits in aquaria – including tanks maintained by private individuals – and Scales traces the history of the aquarium from its origin in Victorian times, when it satisfied the prevailing mania for collecting and categorising. Husbandry of seahorses for aquaria is big business, and Scales mentions a company called Ocean Rider as an example of seahorse breeders. This takes the pressure off populations of wild seahorses, which are particularly vulnerable to human exploitation and pollution because they exhibit such habitat fidelity.

Seahorses are also vulnerable because they have attained almost mythic status in Traditional Chinese Medicine (TCM), and are used to cure all manner of ailments. A chapter on their role as medicine gives perspective on the use of species from both the plant and animal world as medicine – Scales locates TCM nicely in history, tracing its development and explaining the difficulties of testing whether a specific item – such as ground up seahorse – can cure a specific ailment (the holistic approach taken by practitioners of this type of medicine means that each individual receives a very specific, tailored cocktail of medications).

Project Seahorse began in 1996, in response to the realisation that harvesting of seahorses from their habitats was far more widespread and intensive than had been suspected. The project was piloted in the Philippines, and involved the local community – who derived income from the seahorse trade – in setting aside part of the ocean on their doorstep as a no-take marine reserve. The community also allowed researchers to measure and weigh the seahorses that they did harvest, and logged their catch daily for study purposes. The results have been encouraging, and it is clear that involving the local community – who make a living from the resource – in the conservation effort was key. Project Seahorse has subsequently expanded its reach and scope considerably.

Seahorses do not perform a misson-critical role in our oceans; they are not a “keystone species“, and if we remove all of them our oceans won’t collapse and cease to function as ecosystems. In the epilogue, Scales quotes David Attenborough (from page 4 of this interview) as saying that the primary reason for conservation of our natural world is “Man’s imaginative health”.

I can partly support this view, but I think it’s the English literature major in me that’s getting behind it. Certainly, in the case of the seahorse, the greatest loss would be the sense of wonder experienced daily by visitors to the Tennessee Aquarium  and many other public aquaria, scuba divers in Australia, Mozambique, the Knysna Lagoon, and visitors to countless other sensitive locations around the world where these creatures are found. There is, on the other hand, a hint of arrogance in claiming that the primary reason for us not to damage the earth and decimate her species is for our own good. Elsewhere in the interview Attenborough says:

The fundamental issue is the moral issue – and I’ve always said that. The moral issue is that we should not impoverish this world.’

And this, I think, is the point: for us to have arrived, at the end of a process longer than we can adequately comprehend, and behave as though our late arrival gives us licence to wreak havoc on ecosystems that have existed – in balance, without interference – for aeons – is wrong. Just wrong.

Whale sharks are one of the species referred to as charismatic megafauna – species with wide popular appeal that can be used as icons by conservationists and elicit disproportionately strong responses to appeals for their protection. Perhaps seahorses should be listed as charismatic microfauna (I’m not entirely sure that’s a formal name for anything!) – they seem to capture the imagination all out of proportion to their size.

There is much to love about seahorses. You can buy the book here. If you want to read it on your Kindle, go here.


Posted by: Clare | 16 December 2011

Friday poem: The Shark

A far cry from Denise Levertov!

The Shark – Ogden Nash

How many scientists have written
The shark is gentle as a kitten!
Yet this I know about the shark:
His bite is worser than his bark.

Posted by: Tony | 15 December 2011

Newsletter: Dry week

Hi all

Clare and I are in Gaborone, I have not dived in a week and have no idea of the dive conditions from the last week, therefore no newsletter this week.

We leave for home tomorrow and get diving instantly: pool and ocean dives on Saturday, ocean and boat dives on Sunday plus a lot of diving during the week next week. Several students will finish their courses during the week and I will do my best to arrange a midweek launch or two so we can all get on the boat.

Mail or text me if you want to dive in the next week or if you’d like to be on the boat on Sunday. We hope to do the 8am launch from Miller’s Point.


Tony Lindeque
076 817 1099

Diving is addictive!

Posted by: Tony | 14 December 2011

Handy hints: Baboon whispering

In order to become a baboon whisperer, a profound relationship has to be established between you and your furry compadres. How you do this is up to you, but Gerard met with great success after sacrificing (involuntarily) a tupperware full of the chocolate chip cookies his wife had lovingly baked for him.

You can see from the following sequence of images that the relationship between a baboon whisperer and a baboon can be a close and enduring one – much like that between a father and his son.

Posted by: Tony | 13 December 2011

Handy hints: Making friends with baboons

Step one: Fail to adequately defend your dive buddy's vehicle

Step one: Fail to adequately defend your dive buddy's vehicle

Move over, Dale Carnegie. Gerard is here. In order to make friends with a baboon, you need only two things: hubris, and a tupperware container full of Mariaan’s chocolate chip cookies.

Step two: Lose control of the cookies

Step two: Lose control of the cookies

Gerard’s friendship with this large male baboon from the Miller’s Point troupe was hard won, yet enduring (more on that in a follow up post).

Step three: Watch helplessly as your surface interval snack vanishes over the hill

Step three: Watch helplessly as your surface interval snack vanishes over the hill

Unfortunately Mariaan’s little blue tupperware was less enduring, and did not withstand having its lid ripped open by giant baboon fangs.

Step four: OM NOM NOM!

Step four: OM NOM NOM!

(Seriously, feeding baboons creates big problems for both us – humans – and them. There are cases, like this one, where they are simply too quick and too wily to outwit, but do not give them food on purpose. They are wild animals, and feeding them is NOT COOL. Do you hear me, tourists?)

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