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
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!
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
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 statsCitizen 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 statsThe 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
A very important deep skill on a PADIAdvanced course is to compare your depth gauge with your buddy and your instructor. There can easily be huge variations in depth gauges.
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
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
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, 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
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
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
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
Dive date: 8 March 2011
Air temperature: 26-31 degrees (inside the chamber)
Fatally Flawed: The Quest to be Deepest – Verna van Schaik
Fatally Flawed
Verna van Schaik holds the record for the deepest dive on scuba by a woman, to 221 metres in a water-filled cave called Boesmansgat in the Northern Cape. If the name Boesmansgat rings bells, it’s probably because you heard about it as the cave that claimed the lives of Deon Dreyer in 1994, and, more recently, the Australian diver Dave Shaw, who went to recover Deon’s body. The story of that mission is recounted in Raising the Dead (also called Diving into Darkness).
Verna van Schaik was present on the day when Dave Shaw died – she had a critical support role as the person managing all the divers from the surface. She describes her emotions and how difficult it was to know what to do in the situation that arose. Her account of the build-up to Shaw’s dive, the actual unravelling of events, and the aftermath, is fascinating when read in conjunction with Raising the Dead, because she was actually on the team, whereas the other book is written with the apparent objectivity of a third party. Van Schaik criticises Dave Shaw and Don Shirley for going ahead with the dive – she says that they hadn’t slept enough, and that there had been several critical equipment failures the night prior to the dive which made it a desperately risky undertaking.
The book traces her career as a female deep diver. It includes her struggles to be accepted in this very male-dominated sport, her struggle to find and keep a trusted dive buddy, and numerous descriptions of the difficulty of managing a team of divers engaged in high-risk record-seeking endeavours.
She describes the fear she has felt on some of her record-setting dives, and the experience of becoming entangled in her line while at the bottom of a cave, all alone. Very deep dives are of necessity solo dives – there simply aren’t enough people who can and want to dive that deep for buddying up to be an option, and when every single small decision is a choice between life and death, having a buddy can be more of a liability than a help.
Van Schaik does, however, stress that very deep dives require a team of support divers who meet the deep diver on his or her way up from the deepest point. She prefers continuous support (never leaving the deep diver alone during the long decompression) but Shaw and Shirley, for example, planned for divers to be with them only for ten minutes of every hour.
It’s a quick read, could have done with a spell-check, but, especially if you’re familiar with the Dave Shaw story, I recommend it.
We finally did the long-threatened chamber dive yesterday evening. Here’s a video I took from outside the chamber, with Bernita, Goot, Sophie and Tracy inside – highly narcosed at 50 metres and having (from the sounds of things) a whale of a time.
We’ll put up some more detail and photos from the chamber dive later this week.
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...
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
Last week
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
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
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
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.
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.
Into The Abyss: Diving To Adventure In The Liquid World – Rod Macdonald
Into the Abyss
I think Rod Macdonald might be quite famous in his part of the world – he’s the author of several diving guidebooks on Scapa Flow and on wreck diving in England and Scotland. I hadn’t heard of him before I read this book, but I think he’s well-known in British diving circles.
This book is more or less his life story as a diver, starting with his introduction to scuba diving in the early 1980s. The water off the United Kingdom is cold – in parts, even colder than the Atlantic Ocean off South Africa’s west coast. He mentions a dive that they’d do every year in a Scottish quarry on 31 December, Hogmanay, and says that the water was so cold (2 degrees celcius or less) that his regulator would spit pellets of ice into his mouth as he inhaled. When Macdonald started diving, the low pressure inflator hose on BCDs hadn’t been invented yet, so the practice was to descend and then orally inflate your BCD at the bottom. Fun times!
Macdonald soon became interested in wreck diving, and given that the North Sea and surrounds saw so much naval action during both wars, there are many, many wrecks to explore. Navigation during the early parts of the 20th century wasn’t as sophisticated as it is now, so skippers relied on dead reckoning and the locations of many of the ships on the hydrographic charts of the region are incorrect. Macdonald and his friends would search for wrecks using the charts as a guide, and then mark them precisely. Many of the wrecks they dived on were “virgin wrecks” – they were the first divers to make contact with the wreck since its sinking.
Deep diving on air took its toll, and after several scary nitrogen narcosis incidents, Macdonald switched to trimix for his deep diving (shortly after it was introduced – he was among the first divers qualified by BSAC in this new skill). This enabled him to dive deeper, and more safely.
Quite early in his career Macdonald acquired a dive boat, and used this for exploring. His anecdotes about boating and skippering a dive boat are entertaining and fascinating – the insight he has into the ocean from being a skipper as well as a diver is profound.
There are chapters on diving in Truuk Lagoon (MUST GO THERE) and Palau, and the book starts and ends with an account of his incredibly dangerous dive in the Corryvreckan Whirlpool off the coast of Scotland. This is a terrifying natural feature in a deep (70 to 200 metres) narrow channel through which there’s an intense tidal current, directed into standing waves and whirlpools by the narrow pinnacle in the middle of the gulf which rises to within 30 metres of the surface. Macdonald recounts how the downward current at the change of the tide was so strong that he watched the bubbles from his regulator become stationary above him, and then start descending. Scary!
This book was completely different to Deep Descent – I didn’t get the same sense of competitive machismo from Macdonald and his fellow divers as I did from reading about the divers who visit the Andrea Doria. They seem to enjoy the thrill of discovery and investigation, searching for uncharted and lost wrecks. But their diving practices are at the same time very conservative, and on several occasions dives were called off because of the sea conditions (which, off Mud Island, can be dire) or because a diver felt unwell or narced early on in the dive. I approve.
Get the book here if you’re in South Africa, otherwise click here.
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
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
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
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
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
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)
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!
Diving accidents are rare, yet in almost every case stupidity features highly and Saturday’s dive was no exception. We were a group of seven. Three were former students with various qualifications (minimum Advanced), all having done between 20 and 100 dives. All regular divers with me, they were just tagging along for a fun dive. I had three students doing a deep dive for their Advanced diver qualification. All three had completed most of the dives for this course and deep was one of the last dives. I had assessed all three during previous dives and did not anticipate any problems. Cecil, very capable, excellent dive skills and safety concious; Mark, very capable, good dive skills and Diver X, also capable and on two previous deep dives had displayed good watermanship.
So what went wrong?
We descended in a strong current, staying reasonably close together and doing a nice safe slow descent. (I am not a fan of dropping like a brick.) I paused at 20 metres to make sure there were no signs of stress from anyone. Tami was a little slow in getting down but her buddy was watching and of all the group Tami rates high up on the best of the rest list so I was not concerned. The visibility was good, 10 – 12 metres and I could see from everyone’s bubbles that they were all breathing in a relaxed manner.
We dropped to the bottom, and I handed slates to the three Advanced students, slates with a few questions, a bit of maths, and a simple puzzle. This task is a good indication of nitrogen narcosis and a diver’s state. Some of the questions on these slates are ‘”How much air do you have?” and “What is your depth and who is your buddy?”
I time this exercise, so I check my dive computer during the process. This tells me if the depth answer is right, and at the end of the exercise I ask each diver to signal their air supply. Diver X got most of the answers wrong, and more to the point his air pressure answer was 10 bar. I asked him to look at his gauge as everyone else had close to 200 bar. He indicated he did not understand his gauge so I looked at his gauge and it was ZERO.
He then turned and swam away from me towards Cecil, pointing at Cecil’s body. Having someone point at your torso tends to make a person look down to see what he is pointing at. At this point I had caught him up and started to turn him around. He then spat out his regulator and at this Cecil realised there was some problem and perfectly executed the raised arms so his octo was in clear view.
I shoved my regulator in Diver X’s mouth and looked at his eyes – he had no idea of what was going on. I then gathered the group and we started to ascend with Diver X on my octo. At one point I had to bang him on the chest to get him to understand he should hold onto my BCD as he refused to do so and twice drifted off and lost the regulator. We did a short safety stop and ascended. He did not orally inflate his BCD on the surface so I did it for him.
I am extremely grateful to Grant for racing the boat over and getting us out of the water quickly, as we surfaced far from the buoy line (owing to the howling current) and the unexpectedly rapid ascent (and the fact that my hands were occupied holding onto Diver X) meant that we hadn’t deployed our SMBs. The dive site we were at, the wreck of the SS Cape Matapan, is very close to the shipping lane into Table Bay harbour and very exposed. The southeaster was strong and the sea was choppy with fairly large waves making divers on the surface without SMBs very hard to spot.
What do we learn from an incident like this?
Check, check, check your gear. I doubt Diver X checked his equipment before the dive. Second, he did not do a proper buddy check.
Keep your skills sharp. Diver X has forgotten many of the skills he was taught when he did his Open Water course. Refreshers exist for a reason.
Be fit to dive. Get enough sleep and don’t party the night before a dive – SPECIALLY a deep one, where there is no room for error. DON’T come diving if you’re hung over or stoned.
Be alert before and during the dive. Check your pressure gauge before you stow your gear on the boat, when you kit up before rolling into the water, again when you get to the bottom, and frequently during the dive.
And, if you require a dive buddy with exceptional skills, then Cecil is your man.
I know you will all blame nitrogen narcosis for this incident, but on the way up I stopped at 15 metres, again at 10 metres, and again at 5 metres, and there was no change in Diver X’s behaviour. I had to descend from 2 metres back down to the group doing their safety stop and get them all together so we could surface as a group as we were diving on the edge of a shipping lane (I was concerned that we had possibly drifted into the shipping lane in the current) and I had not surfaced with a SMB as I could not release my grip on this diver to deploy the SMB.
What most people don’t realise is that when you don’t take dive safety seriously you almost always put others at risk. I had five other people with me, their safety being my responsibility. We risked surfacing in a shipping lane, without an SMB in less than perfect surface conditions (to put it mildly). All in all other people were put at risk due to the casual disregard for safety by one diver. Don’t dive stoned, hung over or when not serious: not with me and not with anyone else.
I’m left with one cylinder half filled with sea water, one salt-filled pillar valve, and one first stage and two second stages requiring complete rebuilds or servicing. And hopefully some thoughtful divers who all learned something today.
Deep Descent: Adventure and Death Diving the Andrea Doria – Kevin F. McMurray
Deep Descent
I really don’t know if I can recommend this book in good conscience. I devoured it over the space of a day and a half, but it gave me nightmares for several nights running, and when I started thinking about it during the two dives I did just after I finished it, I almost panicked – twice – even though I was in four metres of water at Long Beach.
The Andrea Doria was a magnificent Italian cruise liner that sank in 1956 after a collision with another ship in the north Atlantic. The ship itself was enormous, a work of art, and outfitted with great attention to detail. It lies at over 70 metres depth, an 18 hour boat ride from the North American coast (and thus hours from the nearest decompression chamber). The wreck is subject to howling currents, and as you can guess, the water is freezing. All that said, it’s become a sort of Mount Everest to a particular breed of deep wreck diver, even though the factors listed all place it squarely outside the domain of recreational scuba diving.
McMurray describes the sinking of the ship, but his main focus in the book is the diving that has gone on in the decades since the ship sank. The Andrea Doria attracts a particular kind of diver that I am reluctant to characterise (because I will be rude – but I will probably give in after a few more paragraphs), and there have been fifteen diver fatalities on the wreck. McMurray (a diver himself who has dived the Doria several times) describes the circumstances of several of the deaths, and the other characters involved, in some detail.
As the ship lies in international waters, many of the divers – if not all – who visit her are keen to loot the ship of its china, crockery, fittings, and whatever else they can find. This activity was a contributing factor in the deaths of many of them. I was astounded at the chutzpah with which many of the divers penetrated the wreck – all the guidelines we learned in our Wreck Specialty course were flouted with aplomb. Owing to the depth, it’s very dark down there. The interior of the wreck is collapsing, and as it is a modern ship there is a maze of cables and numerous other hazards to entangle the unwary. In general those who died penetrating the wreck got lost (none of them used reels) or trapped in cables inside.
The depth of the wreck necessitates incredibly complex gear configurations, and in more than one case the diver’s gear arrangement meant that he died inside the wreck. A multitude of clips, pony bottles (two different gas mixes for decompression, plus double tanks on one’s back) and a bewildering array of hoses put all but the most experienced divers under pressure. During a moment of stress, accidentally breathing at depth from your cylinder of pure oxygen (for use at the final, shallow decompression stop) will most likely be fatal owing to oxygen toxicity.
Another danger of a dive like the Doria is decompression sickness – because of the depth, but also because the cold water increases the risk of DCS. The actual bottom time in most cases was half an hour or less, and the depth necessitated extensive decompression on the way up. Divers clipped themselves to the anchor line – the currents and remote location of the dive site meant that getting lost at sea carried with it a significant chance of a lonely death. Inexperienced or unprepared divers who shoot to the surface in such circumstances – whether through a failure to control buoyancy, or (more commonly) either a malfunction in their gas setup, an out of air situation, or panic, are likely to suffer an air embolism and die as their lungs explode. Paralysis is the other option.
I was thoroughly freaked out by this book, but peversely enjoyed it a lot – literally could not put it down. If I’d read it before I started diving, I don’t know if I’d have taken up the sport. The point is, though (and I wouldn’t have known two years ago that this isn’t “normal” diving), that the divers who do dives like the Doria – whether on air (can you imagine the nitrogen narcosis at 70 metres?) or on trimix (where a proportion of the nitrogen in ordinary air is replaced by helium) – are fringe operators, lunatics looking for something that recreational scuba cannot and should not provide. There are individuals who are careful, methodical and motivated by things other than proving a point – whether to themselves or their communities – but they seem to be few and far between. This branch of diving is rightly spurned by mainstream scuba diving magazines and operators.
The sport I do is safe, fun, and non-competitive, characterised by a spirit of co-operation. The diving these wreck cowboys engage in is dangerous, motivated by the wrong things (collecting china so that you can one-up the other divers? I think not!) and characterised in many cases by a competitive spirit, aggression, and a LOT of machismo. There is no place for that kind of carelessness or for any element of competition in recreational scuba diving.
You can get the book here if you’re in South Africa, and here on Amazon.com. If you want to read it on your Kindle, go here. There’s tons more information on the subject on this website, including some pictures that show just how dark and murky it is down there.
I was very nervous before my first deep dive. It actually took a few deep dives before I was comfortable with them, and now I even look forward to them. Mental preparation for deep dives is something you might need to work on – it’s easy for one’s imagination to run wild when it’s an unfamiliar skill.
If you haven’t done a deep dive before, there are some things that you might want to know in advance:
There will be a boat ride. You’ll roll over the side of the boat on the skipper’s count, along with the other divers. Don’t roll over late – rather stay on the boat and let the skipper drop you again when everyone has moved clear. If you land on another diver it’s a good way to ensure you won’t get invited for any more boat dives!
You will probably descend on a shot line. This is a weighted line with a buoy on the end, and the skipper will drop it close to the reef or wreck you plan to explore. You’ll use the line to make sure that you find your dive site – you’ll be descending through a large water column, and a current can easily carry you away from your destination. Circle the shot line gently with two fingers and use it as a guide while you descend. DO NOT grip it like a monkey!
If you’re diving in Cape Town, it’ll be cold. And it’ll get colder the deeper you go. It might even be dark, too. The first 10-15 metres of water may be very murky and green, but down below that the visibility will probably improve, even if it’s dark.
You will feel stupid. At about 25 metres, nitrogen narcosis becomes a noticeable issue. If you feel weird, ascend a bit, wait for it to dissipate, and then resume your descent – SLOWLY. But even if you don’t get it severely, your mental abilities WILL be limited. This is a fact of deep diving on air. You might find your field of vision narrows a bit, that you obsess over things, or that you are very conscious of only being able to do one thing at a time. All this means you need to take extra care, and don’t be reckless. Stay close to your buddy and watch each other carefully.
You will feel heavy at the bottom – no matter how much or how little weight you are wearing. Don’t wait until you’re at 30 metres to start inflating your BCD. Stop at 10 metres, slow your ascent, and inflate your BCD slowly as you continue going down. This way you won’t rocket into the sand at the bottom (assuming there IS a bottom within the range of scuba – not the case if you’re diving a wall) like a cannonball, the chances of severe nitrogen narcosis are minimised, and you can be in control of your buoyancy all the way down.
Colours will be dim and greyish. Take a torch – you may not think it’ll make a difference, but even at 20 metres the reds and oranges are significantly diminished and by 30 metres you just won’t see them at all without artificial light. One of the joys of deep diving is illuminating a very ordinary object and seeing the colours pop out at you.
Swimming will be more of an effort than usual. The water will feel a bit like molasses – thick and viscous. You’re under tremendous pressure, and you simply won’t be able to dart around like a mosquito. Take it slow, don’t over-exert, and move at the speed of natural creatures.
The dive will be short. This is for two reasons: first, you will use your air up very quickly at depth. If it is your first deep dive, this will be especially true – you’ll be nervous, or excited, and you won’t have the experience that enables you to reduce your air consumption. Second, your no-decompression time decreases the deeper you go. So even if you have lots of air, you will only be able to spend 20 minutes or so at the bottom before you have to ascend. If you can’t remember what no-decompression time is, it’s time to revise your dive tables!
You will do a safety stop. Don’t be slack with this – it is absolutely vital. You’ll ascend slowly, maybe stop at 10 or 15 metres for a little bit, and then do a safety stop of at LEAST 3 minutes at 5 metres. Your cylinder will be quite empty, so you’ll be buoyant. Make sure that you control your buoyancy very carefully. Watch the Divemaster, your computer, or the reel on the DM’s buoy line (he may let it hang in the water next to him) to ensure that you stay at a constant depth. Your depth gauge will respond slowly to changes in depth, so it’s not hugely reliable at this stage of the dive.
You might deploy a surface marker buoy (SMB). Your instructor may get you to do this yourself, for practice. An SMB (or as I like to call it, a safety sausage!) is a long tube on a line, usually orange or yellow, that you inflate with air from your octo (NOT your regulator). One end is closed (the top) and one end is open for you to put your octo into and press the purge button to fill it with air. It stands up straight in the water, and warns passing boats that there are divers about to surface. It also shows the skipper of your boat where you are, so that he can be nearby to fetch you. When inflating the SMB, hold onto the line attached to it – not the tube itself, or you might be pulled out of the water with it when you inflate it. Don’t fill it to capacity if you’re still at the safety stop – just a couple of purges of your octo will be enough. As it ascends the air will expand and when it reaches the surface the SMB will be sufficiently inflated to stand vertically out of the water.
Gerard demonstrates correct safety stop technique in Sodwana
In the photo above, note how Gerard is watching his dive computer for depth and while it counts down his safety stop, hanging onto his SMB while he waits to ascend.
There should be a hang tank for you to breathe off at the safety stop. A hang tank is a spare cylinder of air, with several regulators attached. It allows you to complete your safety stop without worrying about being low on air, if that’s the case. It also provides a useful reference for keeping yourself at a constant depth while you’re degassing!
Divers breathing from a hang tank in Smitswinkel Bay
