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The D6 has actually been replaced by the D6i, which is functionally identical but has more internal memory, and is capable of air integration with an optional (heart-stoppingly expensive) dongle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 strap extender, 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.

Update (late 2012): Based on feedback from other divers who have shopped for Suunto computers lately, it seems that Cape Union Mart isn’t doing this any more, unfortunately – but it’s worth asking anyway!

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.

(No) decompression diving

Tony has posted about decompression diving before, but it’s been on my mind a lot lately after the winter diving this year.

If you’ve done a recreational scuba diving course, like a PADI or Naui Open Water course, you’ve learned how to do “no decompression diving”. Your entire dive is structured so that, should the need arise, you could ascend directly to the surface (in other words, without having to do a safety stop or decompression stop on the way up) without undue risk of getting bent. This is why you learn how to use the dive tables or the dreadful eRDP, and why you have time limits depending on what depth you go to. This kind of diving is considered (and indeed, is) far less risky than “decompression diving”, which involves overstaying the limits prescribed by the dive tables combined with staged ascents. This means that solving a problem by surfacing is just not an option (unless you want to create a whole other problem for yourself).

Tony safety stopping at Tivoli Pinnacles
Tony safety stopping at Tivoli Pinnacles

As a beginning diver, it’s often a moot point that you only have x minutes of bottom time at a given depth: your air consumption is usually so poor that the air is gone long before the bottom time is up! As you dive more and more, however, the time limits really come into play and you may find yourself ascending with lots of air to spare, but because your computer tells you it’s time to go.

Particularly on repetitive dives (I’m thinking of a day when I did three long dives to at least 20 metres, all before lunchtime) you’ll run the risk of going into deco (in other words, incurring a mandatory stop on the way up in order to get the nitrogen out of your body tissues). Diving on Nitrox can help a lot with this, and it’s healthier, but there may well be occasions when you do find yourself in deco even after just one long (or deep) dive.

The first time it happened to me I got a bit of a fright. I’d read my dive computer manual back to front and made sure I understood all the warnings and alarms, so I knew exactly what it was telling me, but I wasn’t happy. We ascended a bit, my computer went out of deco, and after my three minute safety stop it gave me the all-clear to ascend. I had an idea in my head that going into deco was REALLY BAD, and I confessed it shamefacedly to Tony on the boat afterwards. He wasn’t too fussed; and as Grant pointed out, “There are worse things than going into deco – like not doing your deco stops!”

A little reflection, however, convinced me that I hadn’t done anything wrong (except perhaps not forseeing that this was going to happen and mentioning it to my buddy, who happened to be Tony!). I’ve done over 150 dives in the two years I’ve been diving, my air consumption is excellent, and I’m very calm underwater. Tony and I know each other well enough that our underwater discussions can be quite detailed. I’ve since allowed myself to go into deco a few times, never more than a few minutes because I dive on a single 10 or 12 litre cylinder, and I’ve done the stops that my computer requests of me (usually only an extra 1-3 minutes plus a 3 minute safety stop). I can tell you that this can be a little boring, unless you have jellyfish and seals for company, or an entertaining dive buddy!

I am very, very glad that I have my own dive computer now, and make sure that I understand exactly what it’s telling me at each point in the dive. I’ve been on a deep dive, and two young divers who didn’t have computers spent the entire dive below me. I went into deco and got a one minute stop on the way up; they must have incurred a much longer obligation, but didn’t know about it because they didn’t have dive computers. If you’re at special risk of decompression sickness due to age, weight, fatigue or other considerations, a dive computer is even more important. Small changes in depth can make large changes in the amount of bottom time you have remaining, and unless you are glued to your buddy’s side all the time, relying on their computer to keep you safe is risky.

Night dive on the Aster

Goot, Tami, Tony, Clare, Gerard and Cecil, ready for a night dive on the Aster
Goot, Tami, Tony, Clare, Gerard and Cecil, ready for a night dive on the Aster

I’ve never done a night dive off a boat before, and never gone deeper than about 12 metres on a night dive, and so it was with mixed feelings that I signed up for a night dive on the MV Aster in Hout Bay, on the evening of 17 September. We’d spent the morning diving in Hout Bay harbour as part of an OMSAC-organised underwater cleanup, and in the afternoon Underwater Explorers was running some boat dives. The visibility on the 2.30pm dive we did on the Aster was passable – not midsummer Atlantic clarity, but a respectable 8-10 metres. I spent most of my time on the deck in the centre of the wreck, on top of the bridge, and around the base of the mast. A strong current was pushing into Hout Bay. The wreck is at about 30 metres on the sand, and the deck is at about 24 metres. The top of the bridge is at 19-20 metres.

A tube worm retracts into its shell
A tube worm retracts into its shell

We launched for the night dive just before 6.30pm. On the boat was Tony, who has done lots of night dives (many off a boat, too), me (who has done lots of night dives, but all shore entries close to the city lights), Tami (ditto), and Goot, Gerard and Cecil, who were all doing their first night dive EVER. I don’t think they realised how awesome they were… Descending 25 metres onto the deck of a wreck, into the 11 degree waters of the Atlantic, in the dark, is something quite special!

The Aster is eerily illuminated by our torches
The Aster is eerily illuminated by our torches

We rolled into the water just before 7.00pm, and descended on the shot line. The first few moments were quite disorienting – it was very dark, much darker than the surface conditions hinted it would be, and it took a few moments for my eyes to adjust and for me to figure out where I was on the wreck. Soon I was more relaxed, and I managed to hunt down the tiny basket stars I’d found on the afternoon dive so that I could show them to Tami. I was glad that I’d done an afternoon dive on the same site – it helped with orientation in the dark, and I enjoyed going back to places where I’d seen things a few hours earlier to check whether they were still there.

Basket star feeding at night
Basket star feeding at night

Tony and I were wearing our Christmas strobes – awesome little gadgets except that the gaps between the flashes can be a bit long when trying to do a quick head count. We also had multiple cyalumes and some rather old glow in the dark Bright Weights (weights is a misnomer here – they are in fact positively buoyant). Those didn’t work too well, but we’re not going to give up on them just yet – perhaps more time under a bright light and/or in the sun will charge them better.

The mast of the Aster at night
The mast of the Aster at night

Doing a safety stop in the dark is a challenge. I didn’t realise how much I rely on having a visual reference – even just watching the depth on my dive computer – to manage my buoyancy at the end of a dive. Using other divers as a reference is not ideal – what if they’re using ME for a reference too? This dive was the first time I’ve used the backlight on my Suunto D6 since I’ve had the computer (about 40 dives), and I realised that the default setting it’s on (illuminates for 5 seconds) is hopelessly and irritatingly too short for a safety stop in the dark. I was also wearing an unbelievably buoyant second wetsuit over my usual Mares Trilastic, which had me shooting towards the surface like a very large cork every time I broke the five metre mark. All this aside, we managed – all of us, together – a safety stop, and then we were on the surface around the buoy, looking for Richard and the Underwater Explorers boat.

The Underwater Explorers buoy on the surface
The Underwater Explorers buoy on the surface

It was very, very peaceful on the surface (until Gerard started on about the crotch strap of Cecil’s new Poseidon wing, purchased for his forthcoming cave diving adventures), and the air wasn’t cold at all. Getting on the boat was a bit of an exercise – dive gear being predominantly black. The boat was far enough from shore that there was very little ambient light to assist the skipper and us in stowing our kit properly, but Richard was organised and quick, and we managed. We had a wait of a couple of minutes for Alistair and his two buddies (all on twins) to surface, and then we headed back to dry land, a warm shower, and the deep sleep that always follows a day of diving.

Tami, Gerard and Cecil waiting to board the Underwater Explorers boat
Tami, Gerard and Cecil waiting to board the Underwater Explorers boat

Dive date: 17 September 2011

Air temperature: 23 degrees

Water temperature: 11 degrees

Maximum depth: 25.3 metres

Visibility: 10 metres (always tough to estimate on a night dive, but we did do a dive at the same site a few hours earlier)

Dive duration: 27 minutes

The divers back on the boat
The divers back on the boat

Dive computers

There are loads of dive computers available today and it can sometimes be difficult deciding what to buy. In my opinion a dive computer should be sold with the required download dongle and the software required to manage your logbook digitally. If you take diving seriously then looking at your profile on a computer adds real value to the experience.

Download cables for the Suunto D6, Mares Nemo Wide, and Suunto Zoop
Download cables for the Suunto D6, Mares Nemo Wide, and Suunto Zoop

Importers also run specials from time to time where the download cable is free which leaves a bad taste in your mouth if you just forked out over R1000 for the cable a few weeks earlier! I am a regular diver so the ability to change the battery myself is an important feature for a computer. Some dive computers require they go in to a service centre (often far from home). After a few battery changes I usually replace the rear cover as well as they tend to become a bit rough once they have been removed a few times. The manufacturer recommends a new cover with every change… but then they would as a battery change costs around R20 if you change only the battery, but around 5 times that for the rear cover.

Citizen

The first instrument for diving I owned, and still wear today, is a Citizen dive watch. It is a far cry from a real dive computer as it records only your last two dives, depth, dive time and water temperature. It does not show you deco or permissable dive time at  depth. Years back when dive computers were very expensive this was a very popular option. It is rated to 200 metres, way deeper than I am ever going and has one downside: a battery change and vacuum seal can only be done in a few places in South Africa and costs around R700.

Aladin Prime

My first dedicated dive computer was an Uwatec Aladin Prime: an easy to use air nitrox computer with terrific software. Only two buttons for all menu options (essentially a four button computer as each button had two pressure points but due to their close proximity to each other a little difficult to use with gloves on). Downloading is easy as the computer has an infrared port as does my laptop but a USB infrared dongle is very cheap if your computer does not have an infrared sensor.

Clare's arm with the Aladin dive computer
Clare's arm with the Aladin dive computer

Suunto Zoop

My second computer was a Suunto Zoop. Again an easy to use (three button) computer with buttons far apart. This was a big drawcard for me at the time. The downside to this is the download cable is not included in the purchase and cost almost 60% of the computer’s price. The software was not as user friendly and the graphics not as good as the Uwatec software, but it still had all the basic information. The computer was plagued for a few years by random shutdowns that never seemed to have any form of regularity. This fault was never found and it sometimes works for month before happening again. This just led to me having very little faith in the unit so it became a backup.

Suunto Mosquito

Next came the now-discontinued Suunto Mosquito, by far the most user friendly computer and a big plus was that the download cable purchased for the Suunto Zoop fitted the download slot on the mosquito. Again it is a four button computer but the buttons are far enough apart that using them with gloves is easy. This computer had one downside for me and that was that it would go out of the Nitrox mode if you did not dive within two hours of setting it. With time the small text has become harder to read at depth (age related eye issue) so an upgrade was required.

Mares Nemo Wide

Enter the Mares Nemo Wide. Four buttons again, but big enough buttons for the aged half blind diver with large screen and big text for the same reasons. This is an amazing computer and by far the best of the lot for me because the screen is easy to read in low visibility and the buttons so large you cannot miss them even if you wear boxing gloves. The software is good and has an easy download interface. The down side was the download cable. Not much more than a mini USB cable with a bit of plastic and a tiny printed circuit with a diode to make it look expensive, this cable costs 60% of the price of the computer which in my opinion is beyond ridiculous.

Suunto D6

Clare dives with a Suunto D6. By far the best in quality, it has a stainless steel housing whereas all the others are plastic. It does have a similar menu and four button system as the Suunto Mosquito but again required the purchase of yet another download cable for a little over R1 000. The software was not useable on an Apple computer so a generic program called DiveLog was found by Clare and she loves it (she will review both the software and the D6 after a few more dives with it). The big advantage of the D6 is the electronic compass so if you do not want to have instruments strapped all over then this is a good buy. Stainless steel is however for more expensive than plastic so take a deep breath when you buy it and make sure it’s strapped on securely!

Citizen, Aladin, Zoop, Nemo Wide and D6
Citizen, Aladin, Zoop, Nemo Wide and D6

Screen protectors

Most if not all dive computers come with a screen protector. Some have it on when you by them whilst others need you to fork out a few more banknotes to obtain them. I found that they would collect dirt and salt between the screen and the protector and with time they become hazy and spoil the view. For my Mares Nemo Wide Clare bought a pack of stick on cell phone screen protectors and we trimmed one to size and stuck it straight on the screen. It seems to last and this is a very cheap option for a screen protector.

Decompression diving

Safety stop on Tafelberg Reef
Safety stop on Tafelberg Reef

As a rule recreational diving is no decompression diving. The dive tables are designed to ensure a huge safety margin and you could ascend directly to the surface (no faster than 18 metres per minute) and in theory you should not get bent. Safety stops are just that: a stop, usually at 5 metres for a minimum of three minutes to allow your body to eliminate some of the nitrogen it has absorbed while you were at depth.

So what if you go into deco?

Should you exceed your maximum bottom time there are a few basics and that is where decompression comes in. A regular safety stop is a deco stop and three minutes is considered adequate on most dive planning, but for example a Deep Specialty calls for a simulated deco stop of 8 minutes with some of this time spent breathing from an alternate air source.

By the time a diver gets to this level of training they invariably have their own dive computer and your dive computer will show you that you have exceeded your bottom time and now have a decompression commitment – usually an eight minute safety stop.

When we do these dives we dive on enriched air/Nitrox and leave at least one of our dive computers on air. The result is that the computer set on air will give you a warning that you are now in deco and it will indicate the length of your required safety stop and the recommended depth. Providing you have planned your air consumption and air supply correctly you will be able to fullfill the deco commitment and surface with your computer ready for  another dive.

Failure to complete the required safety stop for the entire recommended duration your computer will normally not go into full dive mode until 24 hours have passed. By doing the dive on Nitrox yet leaving your computer on air you give yourself  a safety margin, allowing you  to experience the actual computer output screen and interpret what it is wanting you to do, without the risk to your health of actually going into deco and being unable to fulfil that commitment for some reason.

Chamber dive revisited

Sealing the inner chamber door
Sealing the inner chamber door

We recently did a chamber dive to 50 metres. A hyperbaric chamber is a sealable chamber, or pressure vessel, somewhat like your dive cylinder (just larger), and has hatches large enough for you to climb in. It is connected to an air compressor or a bank of compressed air, and once you’re in and it is sealed the pressure is increased just as the pressure around you increases as you descend. You need to equalise as you do under water, the only real difference being is that you are dry. A fast descent means constant equalizing and ensuring deep breaths are taken. You will experience nitrogen narcosis, the extent will vary from person to person and you voice will change.

Our hyperbaric chamber
Our hyperbaric chamber

The video below shows us counting backwards from five, showing the correct number of fingers and turning our hands round after each number. It’s hard when you’re narced!

[youtube=http://www.youtube.com/watch?v=zWX-X5RngUs&w=540]

As a recreational diver you will find that your PADI eRDP will not allow you to enter a depth greater than 40 metres when you plan a dive, and the recreational dive planner (RDP or dive tables) will not allow planning deeper than 42 metres. The chamber operator or anyone that does deep technical diving will have a program to enable proper dive planning and ensuring the correct dive profile is maintained, by means of decompression stops.

Checking on the first group of chamber divers
Checking on the first group of chamber divers

On our dive we descended to 9 metres, and paused whilst two way communication was tested and the operator checked everyone was okay. Thereafter we dropped like a stone down to 50 metres in two minutes. Our bottom time was nine minutes. Nine minutes at this depth gives you quite a decompression commitment and we ascended slowly doing several deco stops on the way up with a total dive time of 39 minutes.

My Mares Nemo Wide showing the dive stats
My Mares Nemo Wide showing the dive stats
Citizen dive computer
Citizen dive computer

Our dive computers all joined us for this dive and were placed in a bucket of water (some dive computers will not go into dive mode unless the water contacts are activated). I had a Suunto Mosquito, a Mares Nemo Wide, an Uwatec Aladin Prime and a Citizen dive computer as well as a wrist mount depth gauge.

My trusty Suunto Mosquito showing the dive stats
My trusty Suunto Mosquito showing the dive stats
The Aladdin that Clare usually wears
The Aladdin that Clare usually wears

The computers were all similar in readings and were all between 50.1 metres and 50.4 metres whilst the depth gauge showed 59 metres! It’s safer for your instruments to err on the side of conservatism (i.e. tell you you’re deeper than you are, rather than the other way around). This depth gauge probably didn’t know what hit it!

Analogue depth gauge with red needle showing maximum depth
Analogue depth gauge with red needle showing maximum depth

A very important deep skill on a PADI Advanced course is to compare your depth gauge with your buddy and your instructor. There can easily be huge variations in depth gauges.

Goot checks his computer
Goot checks his computer

Mares Nemo Wide dive computer

Mares Nemo Wide
Mares Nemo Wide

I have recently been diving with a Mares dive computer called the Nemo Wide.

This computer is slightly larger than my current Suunto Mosquito (now discontinued). The Mosquito is bulletproof and this one has done 1400 dives, had perhaps 6 battery replacements and nothing else has been required in the way of repairs. I have been and continue to be impressed by the rugged reliability it has to offer. However, as age creeps in and eyesight declines reading the smallish text at depth in low visibility is sometimes difficult. The glass is also badly scratched and this also has some effect. I have been fearful of having the glass replaced.

Enter the Mares Nemo Wide. Commonly known at home as ”the flat screen” or (by Gerard) as the “DVD player”, the unit looks rugged and given Mares’ exceptional reputation for quality I do believe it will prove reliable.
The screen, large as you can see, makes reading the data underwater very easy, the menu is very user friendly and the large buttons widely spaced make using it underwater with thick gloves easy. (The Mosquito has small buttons, very close together.)

Diving with the Mares Nemo Wide
Diving with the Mares Nemo Wide

All the basic functions found on almost every dive computer today, air/nitrox, depth and time alarms as well as preferential conservative settings are easy to adjust. The biggest bonus for me is that if set on Nitrox it stays there whereas the Mosquito will revert to air if the dive does not commence within two hours. Working in a busy resort environment I found often that there wasn’t time to change the settings once you were on the go and if I set it early in the morning and didn’t keep track it would be back on air by the time I dived.

Chamber diving for dummies

I’ve been wanting to arrange a chamber dive for a while. Hyperbaric chambers are like large geysers that can be pressurised to higher than atmospheric pressure. They are used in medical applications – breathing oxygen-rich gas at high pressure assists with all manner of complaints – and of course, in diving medicine for the treatment of decompression sickness. They are also used in commercial diver training.

Checking out the chamber
Checking out the chamber

A chamber dive doesn’t involve water, scuba gear or buddy checks. It simulates the experience of breathing compressed air from a cylinder at the bottom of the ocean by putting you in a sealed metal chamber, pumping air into it to the required pressure, and decompressing you slowly after leaving you there for a while. It’s perfectly safe. There’s an intercom so the chamber operator can hear you at all times, and we were supplied with a rubber mallet for knocking on the chamber wall in emergencies while the pressure was being adjusted (which is a noisy process, like sitting inside a jet engine).

Goot settles in inside the chamber
Goot settles in inside the chamber

The chamber we visited is on campus at the University of Cape Town and is used for commercial diver training. Eight of us did a chamber dive to 50 metres (in two groups of four). This is 10 metres deeper than Tony and I are qualified to dive in the ocean (with a Deep specialty qualification), and 20 metres deeper than an Advanced diver is qualified to go. An Open Water diver can go to 18 metres. The only requirement for this dive was an entry-level dive qualification, so Open Water was fine.

Paul the chamber operator at the controls
Paul the chamber operator at the controls

Paul, the chamber operator, checked that none of us had any plates, pins or bolts in our bodies. It turns out that both Goot and Tami are semi-bionic, and they were told to move the affected limb (or jaw, as the case may be) to ensure blood flow throughout the process. Nitrogen bubbles would be more prone to form around a screw or other metal fixture interrupting the natural shape of the bone. We were told to sit with our legs as straight as possible, arms uncrossed, to ensure that blood circulates well throughout the dive. He warned us that if we have a panic attack at 50 metres there’s nothing to do except sit on the affected diver, because once the chamber is pressurised it cannot be depressurised quickly without serious – life-threatening – risk to the occupants. For this reason we had a stop on the way down, at 9 metres, to check that everyone was still happy.

It's crowded in there - Bernita, Sophie, Tracy and Goot do their dive
It's crowded in there - Bernita, Sophie, Tracy and Goot do their dive

The chamber is pressurised to six atmospheres by pumping air into it. The pressurisation was done quickly – it took two minutes (with a brief stop at 9 metres to check that we were all right) to take us down to 50 metres. We had to equalise like MAD, literally every couple of seconds, and the chamber got very very hot inside as the air was pumped in. Boyle’s law at work… Constant volume, increasing pressure!

Starting the ascent
Starting the ascent

We spent about eight minutes at 50 metres. It was an intensely strange sensation. I felt the same light-headed hot scalp feeling that I experienced last time I was seriously narcosed, in Smitswinkel Bay, but magnified to the point that I felt drowsy and woozy and quite chilled. Our voices sounded as though we’d been inhaling helium, and EVERYTHING was very funny. I had a very nice feeling of well-being but wasn’t really interested in complicated conversations.

We had our dive computers with us in a bucket of water, and checked them periodically to see what they were telling us. Tony had his Mares Nemo Wide set on nitrox 32%, and it was flashing at him that we were perilously close to the maximum depth at which it’s safe to breathe that mixture. As expected, it gave us more bottom time than the computers that were set on air before it went into deco.

I distinctly remember trying to interpret the array of numbers on the screen of one of the dive computers, and handing it back to Tony and saying vaguely, “I don’t understand what all these numbers mean” – VERY odd for me because my entire job revolves around the complex manipulation of numbers, and I have a great fondness for statistics of all kinds!

Still feeling rather jolly, and hot - emerging from the chamber
Still feeling rather jolly, and hot - emerging from the chamber

As the chamber was depressurised, we experienced Boyle’s law in the opposite (very welcome) direction: the air cooled rapidly and mist formed to such an extent that at times I couldn’t see Tami, who was a metre away from me. There was a little bit of coughing from irritated lungs at this point!

The first group degassed by spending 5 minutes at 9 metres, 5 minutes at 6 metres, and 10 minutes at 3 metres. This is an extremely conservative decompression schedule and fulfilled all deco obligations plus more after the bottom time that was experienced. All our dive computers would have allowed us to ascend long before Paul let us out of the chamber! The second group, in which Tony and I were, had an even more conservative decompression schedule because of the particular age and physical profile of our group, and we spent 5 minutes at 9 metres, 10 minutes at 6 metres and  a full 15 minutes at 3 metres.

Tracy, Goot, Sophie, Tami, Bernita, me and Cecil - Tony took the picture
Tracy, Goot, Sophie, Tami, Bernita, me and Cecil - Tony took the picture

Dive date: 8 March 2011

Air temperature: 26-31 degrees (inside the chamber)

Water temperature: what water?

Maximum depth: 50.4m

Visibility: wall to wall (so about 1.5 metres!)

Dive duration: 40 minutes

Newsletter: 50 metres and Gordon’s Bay

Hello all you divers

Tracy, Goot, Sophie, me, Tami, Bernita, Clare and Cecil outside the chamber
Tracy, Goot, Sophie, me, Tami, Bernita, Clare and Cecil outside the chamber

We have just come home from a 50 metre chamber dive. We were two groups of four on each dive and the profile went like this: surface to a brief stop at 9 metres to check that everyone was okay and then a plunge down to 50 metres in two minutes, ten minutes at this depth and then around 25 minutes for the ascent with a few stops to decompress.

50 metres down...
50 metres down...

We took a small sample of a wetsuit with us, this compressed to paper thin material. Two balloons, inflated before the descent, shrank to the size of a fist at 50 metres. We took several dive computers and a wrist mount depth gauge. The computers agreed more or less on the depth we reached, 50.2, 50.4 and 50.1 metres. The analogue depth gauge showed almost 60 metres. Great fun and a safe way to experience chronic nitrogen narcosis.

Clare examining the controls of the chamber
Clare examining the controls of the chamber

Last week

Evil-eye pufferfish at Long Beach
Evil-eye pufferfish at Long Beach

We had three good days of diving last week and saw a huge ray, several cuttlefish, puffer fish, and of course the regular octopus. There have also been huge schools of yellowtail, the fishermen were netting a few hundred an hour on the northern end of Long Beach. All the dives last week were interesting as a big school of tiny anchovies followed us around.

Two tiny cuttlefish at Long Beach
Two tiny cuttlefish at Long Beach

We dived at Long Beach on the weekend, Corne doing Divemaster training, Marinus and Dean doing dive three and compass work for their Open Water course, and Sarah finishing her Open Water course.

Dean practising compass work under a towel while Marinus and Corne look on
Dean practising compass work under a towel while Marinus and Corne look on

The water was 15 degrees and the visibility was low, perhaps 3-4 metres. We were able to capture a small feeding frenzy on camera below the bow of the wreck where a few species were after the same food, the winner being the shyshark who took it all in one bite. I’ll send a link to the video in the next newsletter.

Sarah impersonating a manta ray
Sarah impersonating a manta ray

Sunday’s planned boat dives were cancelled due to a red tide hitting the coastline and turning the water into coffee. Clare, Lukas and I did a photography dive to check it out and had less than 2 metres visibility.

This weekend

This weekend will be a little tricky. The Argus Cycle Tour is on and its around the peninsula so there are going to be road closures on Saturday evening and Sunday. Saturday they are closing the road late so we may be able to dive from Hout Bay but will only know on Thursday if this is going to happen.

Sunday is definitely out so we are planning to head off to Gordon’s Bay, weather permitting. The plan is for Grant to take the boat out really early, check out the conditions and then give us a call. You will need to either escape the race, participate, or stay home so why not come to Gordon’s Bay and we go wreck hunting. The diving there is lovely and conditions are good there when our side of False Bay is a mess because of the southeaster. We’re going to make a day of it and have lunch and an ice cream afterwards.

If you want to come diving on Sunday please let me know before midday on Friday because the boat will fill up very quickly with NON-cyclists!

Sodwana

Sodwana divers please send me a list of gear you will require so we can get it planned and arranged. We will have a dinner at our house for the group about 10 days before we leave to get all the final arrangements sorted out. I will let you know amounts owing in a separate mail.

Courses

I am currently running Open Water courses, Deep specialty, Rescue and Divemaster. The Deep specialty qualifies you to 40 metres so if proper exploration of those wrecks in Smitswinkel Bay is on your bucket list let me know and we can do some deep diving.

I am going to run two special programs over the next month, one being a package of Open Water, Advanced and a Specialty – e.g. Wreck, Deep or Nitrox – at a half price. Secondly do Discover Scuba Diving any weekday for R350 and if it is for a friend of yours you can tag along for free.

regards

Tony Lindeque
076 817 1099
www.learntodivetoday.co.za
www.learntodivetoday.co.za/blog

Diving is addictive!

Newsletter: Deep dives, Sodwana, and octopus don’t eat sweets

Hi everyone

Weekend diving

The weekend was not ideally suited to diving and Saturday was too windy for diving. Sunday saw a strong southeaster which dictated the only option for diving, OPBC.

Violet spotted anemones at North Paw
Violet spotted anemones at North Paw

Close to the V&A Waterfront, the boats launched from there and we went to explore a pinnacle close to North Paw. Almost directly in front of Lions Head there is a North and a South Paw, rocky ridges that resemble the lion’s paws.

Cuttlefish at North Paw
Cuttlefish at North Paw

Maximum depth was 25 metres, visibility around 10 metres and chilly water, 8-9 degrees celcius at the bottom. It is a newish dive site so we were lucky to find all sorts of creatures that had never seen divers before. It also looked like lobster country with hundreds of them, all different sizes, all over the place.

Rock lobster at North Paw
Rock lobster at North Paw

Fun with octopus

On Tuesday last week I spent 30 minutes with a video camera and an octopus. I had previously seen this same octopus become very excited at the sight of my brightly coloured weights some time ago. We were doing a peak performance buoyancy dive and when the students placed the coloured weights on the sand near the octopus it became very animated. I spent some time with this octopus last week and gave him some liquorice allsorts to play with. After tasting them all one by one they were spat out. Most entertaining. Watch the video here.

Night light sea jelly with Tony in the background
Night light sea jelly with Tony in the background

Deep Specialty

This weekend we start a Deep specialty course. As a deep diver you are qualified to dive to 40 metres, this makes many of Cape Town’s wrecks accessible for exploration (including those in Smitswinkel Bay, most of which are deeper than 30 metres on the sand). Experience an emergency decompression stop, navigation at depth and breathing from a hang tank. You will learn more about nitrogen narcosis, how to plan a dive using a dive computer and the use of dive computers. Drift diving and wall diving will also be experienced during this course. You will also learn proper deployment of an SMB. If you’re interested or want to discuss this course with me, drop me an email.

Cecil checking his computer at a safety stop
Cecil checking his computer at a safety stop

Congratulations to…

The following students have attained their qualifications since 1 January – welcome to the world of diving!

Open Water -Arieh, Michelle, Andrew, Lukas, Jamie-Lee, Danelene, DC, Sarah (all grown up)

Junior Open Water – Shira, Josh (nearly grown up, 10-15 years old)

Seal Team – Abby (9 years old)

Advanced – Oscar, Mark, DC, Cecil

Nitrox – Cecil

Tony, Cecil and SMB on the surface after the North Paw dive
Tony, Cecil and SMB on the surface after the North Paw dive

Plans

Wednesday and Thursday I am doing some Rescue training and an EFR course, a prerequisite for Rescue.

We will be finalising the arrangements for the chamber dive this week, and I will contact those of you who have expressed an interest in a separate mail. If you’d like to take part and haven’t let me know yet, or want to know more about it, please email me.

I’ll also be in touch about Sodwana (16-20 April). If you’re still on the fence or still need to pay your deposits, get moving and confirm whether you’re in or out.

And finally, permits – if you don’t have one, go to the post office NOW and get one!

regards

Tony Lindeque
076 817 1099
www.learntodivetoday.co.za
www.learntodivetoday.co.za/blog

Diving is addictive!