BLOG: What I wanted to say…
Gas planning tool
New toys: I have tinkered a bit and now have three small new tools for gas planning – here to try out and discuss.
This is NOT intended for complex deco dives, if you are planning a complete dive anyway, you have a gas planning in Subsurface or other tools that is much better tailored to the specific planning. The tool is intended to help those who only use “we’ll stay at 30m until 3 minutes before the no-decompression limit” or similar as a dive plan. That’s enough IF there’s enough to breathe – and the tool is designed to help you think about that.
Minimum gas calculator
| Parameters | I | Use standard? | Buddy | Use standard? |
|---|---|---|---|---|
| AMV (L/min) | ||||
| Bottle volume (L) | ||||
| Stress factor depth | ||||
| Stress factor ascent | ||||
| Maximum depth (m) | Pressure (bar) | |||
| Time to solve the problem (min) | ||||
Who is afraid of oxygen?
One of the most important things you learn in every Nitrox course is that you can get an oxygen toxicity hit at high oxygen partial pressures. This can lead to seizures, which are difficult to survive under water.
That’s true, without a doubt, and we definitely don’t want to take that risk. But what actually has to happen to get really close to the limits? And what side effects does the fear of oxygen toxicity have on divers?
When do the seizures start?
The most feared of the “OxTox hits” is the CNS Toxicity. Excessively high pO2 leads to central nervous system problems such as impaired vision and hearing, dizziness, a metallic taste in the mouth, sensory disturbances – and ultimately to convulsions.
A seizure under water is a very serious matter: breathing can no longer be controlled, the whole body twitches or stops moving altogether – such a condition is more than just unpleasant on land, under water it is likely to be fatal.
That is why we want to avoid this symptoms under water at all costs. We therefore stay far enough away from all recommended limits – preferably as far as all our diving associations recommend: For normal dives with Nitrox, 1.4 bar pO2 is considered safe; for prolonged exposure such as with a rebreather, 1.3 bar or less is more likely to keep you below this limit.
In dry conditions, e.g. with pressure chamber treatments, the values look completely different. Breathing pure oxygen at 18m? No problem, this is done regularly. The seizures that sometimes occur are accepted for the success of the treatment. But you are sitting on dry land, where the probability is much lower than when you are moving under water – and the result is not dramatic.
But you can already guess from this: Unfortunately, the limit values are not empirically substantiated by any stretch of the imagination, and the “CNS clock” is repeatedly criticized. Because the mechanisms of how oxygen toxicity leads to symptoms are not fully understood, and because these reactions occur so chaotically and unpredictably, determining limits is more guesswork than science.
Nevertheless, these limits have proven their worth over the years. Within these limits, you can be nearly absolutely certain that you will not experience oxygen poisoning. The NOAA limits, also known as the “CNS clock”, have now been used successfully for decades and appear to have made oxygen toxicity accidents extremely rare.
So you can feel safe within the limits, but the reverse is not true: if you exceed them, you will not be struck by lightning or oxygen toxicity immediately. It’s just that the risk is increasing and we don’t normally want to accept that. It’s a bit like the M values – you have to draw a line somewhere, but it’s not a hard limit, it’s set somewhere in a vague area of increasing risk.
The big problem with CNS poisoning is that it is unpredictable. In most cases, the symptoms appear very quickly under water – or we don’t know exactly whether anything was felt beforehand because the victim can no longer report.
It is known from pressure chamber experiments which symptoms occur before the cramps. Experiments published in 1947, in which people were exposed to oxygen in a pressurized chamber at over 3 bar for so long that the first symptoms became noticeable, are still used today. This also resulted in a few seizures, so the experiments were somewhat dangerous. That is why we are still using these very old results today: There is no reason to repeat experiments in which people are harmed, and certainly not when new results are not even expected.
From this source comes a graph of CNS toxicity that shows very clearly how chaotic its occurrence is. What becomes clear here: In one and the same person, symptoms of oxygen toxicity can occur after extremely different lengths of time. It is neither trainable nor in any way predictable how long it will take on any given day.
What does that mean for us? Because it is unclear exactly when the symptoms will start, a very large safety distance from the area in which this can happen is appropriate. On the other hand, you can also see that the symptoms do not start with the first few breaths. This is also logical to a certain extent: the oxygen first has to get into the body and start doing unwanted things, and that takes a few minutes.
For further reading: DONALD: Oxygen poisoning in man. 1947
Are OTUs a thing?
First of all: No.
Not for us at least, if we do a few dives a day within the no-decompression limits with Nitrox. This can be different for treatments in the pressure chamber and also for very long rebreather dives.
OTUs, Oxygen Toxicity Units, are a unit that can be used to determine how long someone can breathe oxygen at a higher pressure than normal without damaging the lungs. There is a fairly solid database on this, and if you want to continue to have functioning lungs, it is wise to stick to the recommended maximum values. At 300 OTUs a day for several days in a row, or even 850 a day for individual days, they are always very high.
For recreational diving, we therefore have another limit: the CNS clock. If we stick to them, we won’t care about the OTUs – as you can clearly see here in the table.
At what point does the pO2 become a problem? So, all in all?
One could now come up with the idea that our limit values are very conservative. If people don’t feel any symptoms for a long time even with a pO2 of 3 bar, why then our narrow limits?
Quite simply, the limits used to be somewhat wider, at 1.6 or even 1.8 bar pO2. Over time, however, it has become apparent that oxygen intoxication does occur in this range from time to time, especially when other things such as exertion are added to the high pO2. And you can’t rule out having to make an effort when diving.
Accidents in which oxygen poisoning plays a role are now very rare – and the few that do occur are surprisingly easy to explain. There was the rebreather diver who simply raised his pO2 to 2 bar – which worked well for a very long time, long enough to feel safe and always do it that way, because there was much less deco…. Until it just didn’t go well any more. Because it is not possible to predict exactly after how much time it will happen, but at such a pO2 it will happen at some point. And then there are always mix-ups during technical diving: If you accidentally switch to pure oxygen instead of EAN50 at 21m, things can go wrong. Incidentally, you can also be lucky and nothing happens. But under no circumstances should you start convulsing with the first few breaths – perhaps the confirming look at the buddy’s gas after the gas change is much more important than watching the action. But that’s just a side note…
Accidents involving oxygen poisoning in normal recreational diving with nitrox, where all limits have not been exceeded grossly and over a long period of time, no longer occur. As long as you know what exactly is in the bottle and stick to the 1.4 bar pO2, you really don’t need to worry. Not at all.
OxTox panic: The biggest risk?
Nevertheless, the fear of oxygen toxicity is great and widespread. How many of you have heard it before – that guide who proudly tells you that he won’t go any deeper than so-and-so because he has Nitrox and would surely be poisoned?
Who has ever been asked whether it would be better to take two days off because MOD flashed on the computer?
Apart from the absolutely irresponsible behavior of a guide, it is simply not conducive to a relaxed dive if you are constantly afraid. Fear can turn into panic at the slightest problem – and this is REALLY dangerous underwater. So what should we really be afraid of, and what should we not be afraid of?
We have seen that you rarely get problems below a pO2 of 2 bar. Rare is not enough for us, because you can usually survive the problems on land – but not under water. To go from rarely to never, it makes sense to set the limit at 1.4 bar pO2.
This means that even at a pO2 of 2 bar, it is unlikely that someone will convulse in the next moment. But yes: it can happen from then on.
Our limit values are chosen so that we still have a few meters of leeway. But they are there for exactly one thing: Emergencies. They are NOT part of our dive planning.
I plan my dives with a pO2 of 1.4 bar at the deepest point OC, 1.3 bar pO2 CC (where you are exposed to this pO2 for longer). For deco, at moderate to shallow depths, I then go to 1.6 bar pO2 – for a limited time.
But the panic thing – it’s really important to know that the limits are not rigid. You do not suffer poisoning at a certain dose inmediately and automatically. So if there is an important reason to cross the border for a short time, you can do so. Of course you can help your buddy if you have to accept a pO2 of 1.7 for 2-3 minutes until you ascend together.
It’s difficult to say exactly where to set the limit – but if we plan for 1.4 bar pO2, we always have a margin.
Experiencing a very high pO2 for a short time is almost always good. Only a longer exposure time causes problems. If you had a pO2 that was too high, you should reduce it afterwards, i.e. increase it a little (or change the setpoint on the CCR)
But the most important thing is: DON’T PANIC!
For the few minutes on the outer reef….
Malpique: Where the soul is lost in black coral
A friend once wrote to me that he had lost his soul at some point on the outer reef of Malpique and has been searching for it ever since. Still and again, it pulls him there just magically into the depths.
Arguably lyrical, but fitting nonetheless: few places in the world have such an attraction for me. In that one deep crevice where the barracudas hide – I think a part of my soul got stuck there, too.
The tower of Malpique, from below. Mystery, goal, signpost.
When you meet Malpique….
… then probably the first thing you see are the crosses, the canyon, maybe the wall, and if you dive really well the arch. Beautiful, fascinating – and the dive through the blue to the tower, feasible for normal sport divers, can already take off your shoes. For the technical divers, another dive site starts here.
Where the recreational depth ends, so does the tower, this lava monstrosity overgrown with black coral. From one side it looks like a heart, from above like a needle, as a shadow in the blue like a vague signpost. As such, you leave it to the side when you head for the outer reef – the really outer one, still far below the arch. And here you end up at a wall whose end is not visible. 50m, 60, – the view wanders deeper and deeper, into the endless blue. In a crevice stands a school of barracudas, guarded by a large amber jack, sometimes chasing back and forth or swimming in circles. It doesn’t take long, then you have to go up again.
The blue downward is in fact not endless at all. At 90m it turns into sand. From down there, the view up the cliff face is incredible: over 30m, the forest of black coral lies vertically on the cliff face. But you can not stay, it is only a few minutes that we may be guests in the depths.
But how do you get that deep?
Back then, when divers were still strong men with beards, when parents smoked with their children in the car, well, back then, of course, people already dived out there, with a single bottle on their backs, and without a computer, and most of the times that went well. Most of the time, at least.
Today, much has changed, and really often for the better. Also the safety thinking in diving: We want to be sure to resurface, and we want to resurface even if something goes wrong or we make a mistake. That’s why you don’t just do it like that anymore, but slowly move deeper with proper training. And every, really every single step of this approach is worth doing in itself.
“Just a little decompression”
The old hands like to claim that a bit of deco is part of the basic training and that you should just do it. You learned how to “calculate” deco dives anyway. Unfortunately, they often mean nothing more than that the person can read off a decompression table.
Others, however, the gods of tek, are convinced that from 30m onwards, trimix, a redundant gas supply, a long hose and two knives are needed. Everything always configured the same for everyone, of course.
I am quite sure that you can do both and much in between: dive the tower sometimes with mono cylinder, sometimes with trimix, sometimes with mono cylinder without octopus and sometimes with D12 and three stages in the water, or even with rebreather, several bailouts and scooter – it all works.
But what you should clarify if you want to do deco dives:
- Can I handle problems underwater without surfacing and without grossly losing my buoyancy?
- Do I have enough breathing gas with me to make the dive and handle any potential problems?
- How high a risk of decompression sickness do I accept, and how do I assess the risk?
A few minutes of deco is not a technical dive…
Even today, you don’t have to become a complete tekkie just to hang out for a few minutes. There are trainings at the different federations to do deco dives and to use a deco gas. This brings you a whole step further, but you don’t have to change your equipment completely. At SSI this is the “Decompression Diver”, other associations have similar courses.
Somewhere, though, that has a limit, usually set at dives above 40 meters. The reason for this: the breathing gas supply and redundancy.
Want to dive deeper
If the 40m are not enough, more gas will be needed at some point. A double bottle on the back, or one on each side – just so it can withstand a rock bottom calculation. And you have to know your way around gases: Oxygen can be nasty, and you also have to like nitrogen.
With double equipment and two stages you can go far – but at some point, especially when helium prices come into play, even that reaches a limit. Then you think about just breathing the same gas over and over – the rebreather is suddenly sitting in the back of your mind, grinning happily at you.
Clear in the head: Trimix
It’s beautiful, really beautiful down there. But you usually don’t really remember what you saw during deep dives with air – the ones that are perhaps too deep. It was a bit gray in any case….
These are very clear effects of nitrogen narcosis. Once you are in the same corner with Trimix, the colors come into play: you can now see how the column continues, see the red and the green and the contours become clear again…. Those who first change at the bottom can experience how this veil is lifted. Kind of like what you can feel when you dive deep with air on the way up.
Of course, the stuff is expensive, horribly time-consuming, and only for a few minutes of bottom time – but, yes, really: it’s worth it.
What you put up with
All in all it is a long way to the bottom of the outer reef. A bottle on the back, and off into the water? It’s not that simple anymore.
Dives with gases you can’t breathe on the surface take a lot of planning and a lot of preparation. First of all, we need a dive plan: Where do we want to go, how long, what gases do we need? They then have to be mixed, the equipment may have to be adjusted again, and only then can we get started. So, after you manage to actually be in the water with all the equipment. And you know you have to get out too….
But then you look up from below. Directly below you the sand at 90m, above you this wall that you have always only glimpsed from above. Vertically upward, you emerge again, toward the sun shining through the fir trees. At 60m you feel at home again, flat, almost at the top. And remember how deep it felt just two weeks before, with air.
Then, at that moment, I had to think about rebreathers. I have since been able to see the area and a few others with my JJ, and it was the best decision I have made in recent years. But that will be a new story.
Become a Divemaster: Pay for course in cash or in labor?
The business with dreams
The reality is different, and everyone who has ever asked a little more knows that. As a divemaster you can only find a job in a few places anyway, you are poorly paid – and it doesn’t get much better as a dive instructor. To really get a foothold in the business, you have to have more to offer than a Divemaster card.
Nevertheless, simply doing what you really want to do and sharing that passion with others can be one of the best decisions in life. If you really, really want it, you can make it even in diving. And just the fact that you get to dive while you work compensates for a lot. It doesn’t have to become a career for the rest of your life.
All evil…
Now, when it comes to how best to become a diving professional, the first big debates already start. At least, if you dare to ask on facebook or other forums….
In the German-speaking world, the main criticism is about the evil bases that exploit poor novice divers as trainees and do not pay them at all for their valuable work. Americans seem to see it differently, they rant and rave about the impudent divers who don’t want to pay for their divemaster, but earn it with an internship.
So who is evil – the base operator or the future divemaster?
As always, it depends. Basically, diving costs money, and proper training even costs quite a bit of it. If an education is too cheap, the suspicion is that it cannot be good.
Those who pay for their courses have the right to insist on the agreed service and, in case of doubt, can change providers without much effort. So, if you are earning normally in a normal job, it is definitely a good idea to just book the courses you want to do.
But those who earn little can also find offers to pay for the courses with work. Here, too, payment is made, but in a different form. And that can look very different.
Training versus collaboration: What should you look out for?
Basically, the work you can do as a trainee on a base is unskilled work – in other words, nothing for which you are paid princely wages. So if an offer sounds too good, you should become suspicious. No base gives away their training, the more you get, the more meaningful work is expected for the base. At best, this can mean spending more time at hotel pools selling try dives than in the water yourself, and ending up knowing the compressor room better than the house reef – but at worst, it can also mean being assigned as a guide or even an instructor:in far too early. Asking what tasks you are asked to do and how many dives you can usually do yourself is definitely a good idea.
But to do this, you should also adjust your own expectations. No, you can’t guide with 30 dives, yes, introductory dives are challenging and you have to be qualified to lead them. You’re doing the training to learn how to do that, and you should be able to do it at the end, not kind of do it from the beginning.
And even if it feels like you’re working ten hours a day, six days a week: Take a close look at how much of that time you spend doing activities relevant to the base. When you go diving twice a day, there’s not that much left….
Exploitation at its finest: the most chilling examples
Life as a trainee can indeed be quite disgusting. If you get the wrong base, you’re the lowest in the base hierarchy, allowed to clean, fill bottles – and maybe dive once in a while. It is terrible when trainees do not get into the water, do not gain any diving experience or training for months, but only serve as unpaid unskilled workers. If they then end up being given a certification for which they haven’t even done the training, it doesn’t make things any better.
But even worse than this exploitation is when trainees are used for instructor duties. In many bases it is common practice that the still very inexperienced divers already guide guests and even conduct introductory dives – as the most extreme case known to me the young man with just over 20 dives, who was alone with six (!) introductory divers in the sea.
The best internships
But since not all bases are evil, there are of course examples of how things can go well. Ideally, you will be in the water a lot during an internship and get the full program of basic everyday life. 30-40 dives a month, accompany introductory dives and courses, function as a reliable buddy, find your own way, then guide yourself under observation, observe different instructors and be able to pick out the best – that’s how you learn. The more time you spend with it, the more real experience you can gain. Even the best course can’t give you just that: Experience. You have to do them yourself, and for that a longer stay in a dive center offers good opportunities.
Therefore, many bases offer internship programs that you have to pay for as a candidate:in. Sure – in that case, you’re not used for basic activities, but everything revolves around how you learn best. Whether paid or on a stipend, spending as much time in the water as possible, with a healthy mix of dives that are challenging for you and dives where you watch beginners make their first steps, is the best way to learn.
Internship with us
Especially young people often simply do not have the money to pay for many dives and a reasonable training – but time without end. That is why, when we have just need of guides for the next season, we offer a realistically cheap to in the end almost free option. “At the end” because first the course is paid. But you don’t just learn the standard program in the course, you slowly get to be responsible for all the basic work in the team like everyone else. You don’t just do a few training dives, but dive as often and as long as you want. You usually join the dive where it makes the most sense – even if something else would be more fun.
If you have the time, you can really study hard and get to the point where you can actually work for us as a guide. And then this is where something comes back: the moment we can actually use someone independently, that’s when we get paid. In this way it is possible to “earn back” the course, so to speak – but because this depends on the one hand on the volume of customers, and on the other hand very much on the guide, we do not make too big promises.
Those who earn normally are probably better off just booking the courses and lying in the sun after diving instead of filling the tanks. So that the experience does not come too briefly, we offer nevertheless that everyone, which makes a Pro course, can dive as long as he wants with us – and in each case with that, which brings them straight further. The advantage to a paid course is clearly that your education is the focus, not the needs of the base – you don’t work here, you are a guest.
… and it is fun after all
With all warnings, and all caution: Of course, we all do the job because we enjoy it. Again and again, still, for years. Everyone who’s been around for a few years has a lot of annoying stories to tell – but some good ones, too. And over time you find out if, how and where you would like to work. I’ve been doing nothing else for 15 years now, and wouldn’t trade my life for a normal job for the world.
Where are the best dive sites in the Canary Islands?
Atlantic? Diving? Really?
Many divers love warm waters, with their colorful tropical fish, coral, white sand – and sure, that’s nice. But, quite honestly: I get bored relatively quickly. Somehow I get attached to the black sand, the lava rocks and this intense, clear blue.
The Atlantic Ocean always provides new surprises, and that’s what makes it so interesting. Sometimes the biggest ray ever passes very close, a manta ray makes its way up dark (every two years), sometimes there are a lot of trigger fish on one spot, then suddenly none, but butterfly rays – on every dive it is different than a few days before. That’s exciting, that’s what I love about the East Atlantic, and especially here on La Palma on the steepest of the Canary Islands.
The Canary Islands: Seven islands, seven worlds
Each of the Canary Islands has its own charm, under and above water. What they all have in common is the volcanic origin, the rugged landscapes, the jagged rock formations under water. No corals, but colorful sponges, caves, dark and light sand, steep walls and lava flows.
If you vacation often enough and like to see something new every time, you may well just visit one island after another. My personal ranking: No 1 is La Palma, closely followed by El Hierro, then comes directly already Lanzarote. Tenerife and Gran Canaria in the midfield – they are also just too big and too touristy for me. Oh yes, and then there is Fuerteventura….
Fuerteventura – ah, Fuerteventura…. There are said to be people who love this island, especially surfers. I never understood that. Diving can be done in the north in the shallow area between Lanzarote and Fuerteventura, there may be some nice spots. Then in the middle there is the long wall in front of Caleta de Fuste, and in the south the big and the small moray reef. Honestly, I find the island as boring underwater as it is on land. Probably simply because I lack variety and depth.
At Gran Canaria it is said to be good for diving. I have not been in the water there yet, but I have observed how it is done at “El Cabron”, the most visited shore diving site. This is a rocky entry, nasty, wavy…. And the guides here have developed their own method of getting people in and out of the water. JENS, NOVH TIMES EXACTLY PLEASE!
Tiny La Gomera is not exactly known as a diving destination. I also just enjoyed the forests and mountains there – the island is so beautiful, it would be worth just trying it out.
The very smallest of the Canary Islands is El Hierro, and for mainland Spaniards this island is considered the diver’s paradise par excellence. That is why in La Restinga there is one diving center next to the other. Diving is always from the boat and the sites are indeed spectacular. The chances for big fish are better than on the other islands, the often clear currents seem to be quite attractive for many animals. The only drawback is that there is only one small local airport, so getting there is a bit of a hassle.
And then there is La Palma. That the greenest of the Canary Islands is my favorite will surprise no one. There are several reasons for this. La Palma is incredibly steep, so even in the water it gets very deep very quickly. You can walk comfortably from the beach into the water and shortly after you are at any depth you can imagine. Since it is also beautiful in the shallows, even beginners get their money’s worth – and the very hardcore can also watch colorful fish while decompressing. In addition, the dive sites are more diverse than I have experienced on any other island. So it remains exciting for a long time, and there is always something new to discover.
Diving in the Canary Islands is adventurous
If you dive here, you have to haul your own equipment, rinse it yourself, and often load the jeep or boat as well. There are just no cheap slaves, and you do not really want to pay the service at the European minimum wage…
There are also waves, surf, sometimes current. All no problem if you listen to what the guide says about getting in and out. Otherwise, a bit of rolling in the surf can be quite funny – at least for the spectators…
But most of those who get involved once keep coming back. Because it’s close, warm, yet European, and you can just dive awesome. And it does not get boring even after thousands of dives.
