For a quick and dirty definition, you might say that planning for a technical dive is mostly about working out how to deal with contingencies when something hits the fan.
Of course that definition does beg a few questions: for example, exactly which contingencies does one have to deal with during a technical dive, and how fast is the fan likely to be spinning? But as a starting point, and in particular when trying to explain what the sport is all about to someone who is neither trained in nor familiar with technical diving, it works as well as anything else.
One of the first instructor-trainers I worked with was extremely fond of charts and graphs. His students left his workshops and classes with the impression that he had pie charts, bar graphs and spread-sheets of stats for almost everything related to diving. He could tell you what percentage of aluminum 80 cylinders made in a particular year by one or two manufacturers were painted red; or the total number of snorkel keepers that sat unused in the bottom of save-a-dive kits world-wide; or how many open-water divers out of a graduating class of, say, 100 would go on to become dive masters. Totally worthless information in most instances, but what it lacked in usefulness was compensated for in a perverse way by him having lots and lots of it.
Naturally and in accordance with the laws of nature, hidden away among the chaff were a few kernels of useful data too. For example, he had a chart showing the average number of catastrophic gas emergencies year by year per 1,000 dives by certified cave divers.
Much to my disappointment, I am unable to remember any of those figures – useful or otherwise – and in any event I was reasonably sure at the time of first hearing that a good percentage of his data were suspect and most probably thrown together the evening before he was due to share them with us – his eager new instructor candidates. I believe a good number of them were creative artifacts crafted in-situ, so to speak, to add an atmosphere of scientific sincerity to his otherwise wildly entertaining, right-brain presentations.
However, what I can remember was a favorite phrase he used when outlining for us what was involved in his version of contingency planning – “covering your arse” – whether diving on our own, with buddies or with students.
“You can, without much real effort,” he would say. “Contingency yourself right out of the water, and quickly arrive at a point where any and every dive looks too risky to undertake…”
During one presentation, he said: “Let’s take as a given that poor safety engineering in life-critical systems such as low-cost scuba regulators is reasonably commonplace.” He explained that based on the average diver’s yen to save a buck on kit, you could easily create a hugely pessimistic risk assessment for that average diver: especially if you wanted to factor in bad habits like not doing proper pre-dive checks.
Following that logic, and considering the magnitude of loss associated with diving accidents (the threats of death by drowning, embolism, oxygen toxicity, severe decompression sickness, et al) any argument that the probability of said failure is unlikely was smothered.
“Quantitative arguments about kit being unlikely to give up the ghost and go pear-shaped,” he told us; “Are moot if we were to agree that the common human reaction to component failure is panic: and since we cannot reduce instances of component gear failure to zero, and panic usually results in death or injury, diving is unsafe and should never be attempted.
“Clearly this is, to a great extent, bullshit,” he said, “Otherwise we would have to wade through a slurry of dead people at every dive site we visit. But it’s worth noting that people die sometimes for no better reason than they were surprised and unprepared.” He wrapped up the lecture by explaining that the secret is to know what has the shortest odds of actually going wrong on a dive and focusing one’s primary efforts on that, but also being prepared for the unexpected.
A rational and reasonably careful look at the situation makes it obvious that all the threats presented by diving can never be eliminated. So if we want to dive, we have to learn to be happy with an action-plan that deals primarily with threats that are real and that might actually happen. And when we have that sorted out, and before venturing deeper and longer than a sport dive, we should include cover your arse strategies for the unusual… because Murphy is a devious bastard.
I should admit that I am lazy. If there is an easier way to be effective, I’ll find it; and if it’s possible to reuse something again and again until it’s frayed and worn thin, I do so without much hesitation. There are some provisos but those are my guidelines… especially for contingency dive plans.
I am a huge fan of using and reusing the Apex Dive concept. The definition of apex dive that I use and teach is that we can separate various dives into categories by considering the equipment and training required to do the dive. To some extent, the depth and gear limits outlined in most of the technical dive programs I teach, help to draw hard lines around the otherwise ill-defined concept of a “Technical Dive.”
For example, one category of apex dive is for an open-circuit staged decompression dive in open water from a “starting” depth of 30 metres (100 feet) to a maximum depth of about 45 metres (that’s around 150 feet to my non-metric American and Canadian friends). If we add to this the limits we accept is we will use one decompression gas and work within the gas volume rules for only two cylinders of bottom-mix, we have defined the apex dive for graduate from a TDI Helitrox Decompression Program.
I have written down and available in my kit a “simple” action plan for this level of dive, and it includes set waypoints, maximum duration (given a specific minimum starting gas volume), ascent schedules, bailout schedule, lost gas plans, bailout scenarios, what to do if various pieces of kit fail, how to and how long to conduct a search for a lost buddy, how to bring an injured or unconscious buddy to the surface, and so on and so forth.
This apex dive plan is designed to be used with ANY O/C dive at this level or shallower and shorter. I use a similar approach to other categories of dives to greater depths (60, 75, 85 metres for example), and shallower (to depths of only 30 metres specifically), and for dives in different environments such as caves. I also have a similar array of plans for similar dives on a closed-circuit rebreather.
Much of a plan laid out at one level, is almost exactly the same as the plans for dives at the level below or above. The gas management plans, ascent and bailout schedules change of course, but a lot of the scaffold keeping the plan upright, is common across the board. Also for each of these dive plans there is a segment you could call the “it’s been a really bad day” scenario. The situations covered in this are the ones that are unlikely to occur, but which carry with them, a really serious magnitude of loss.
Some of these situations are the “contingency yourself out of the water” scenarios that my old IT told his classes about. Notwithstanding his advice to “ignore the unlikely,” it seems prudent to me to have something in place to deal with several of the unlikely possibilities when diving deep and long.
For example, I have nothing that will help me deal with a lightning strike while hanging on a decompression line, but I do have a plan to help get me back to the surface with a broken buoyancy device. As unlikely as it is that a wing would spring a catastrophic leak underwater, most wings used in technical diving do have a ludicrously venerable weak point: the 15-cent plastic elbow that connects its inflation hose to the body of the wing itself.
While judicious handling during transportation, a good assembly and pre-dive inspection, and a bubble-check before descending can all help prevent this particular failure, losing a wing at depth would be serious, and in most cases could really ruin your day.
At some point in the past, you have probably heard the advice to dive a balanced rig. A balanced rig is, according to a definition just read on Wikipedia and a couple of diving websites, a rig that a diver can swim to the surface from depth without the help of a wing/buoyancy device when the cylinders are empty because it will then be “neutrally buoyant.” Someone with a rudimentary understanding of dive kit and basic physics might read the previous sentence and tell themselves: “yea, sounds legit.” The rest of us may be left with some nagging doubts.
For example, what’s with that “neutral with empty cylinders” nonsense? I am a fan of divers NOT getting into the water with too much ballast but cylinders are never empty and since whatever gas is in them has mass, surely in a balanced rig/broken wing scenario, gravity is going to win.
In my opinion, we need some alternative to swimming our kit and ourselves up from depth without ANY assistance. As luck would have it, we do not have to look far for some solutions.
Unlike most sport divers, few open-circuit technical divers have truly ditchable weights. Their ballast is supplied by integral items of kit such as steel primary cylinders and a stainless-steel backplate. Sidemount divers may have the option of dropping one primary cylinder if needed, but divers wearing back-mounted doubles do not. Therefore, in the event of a wing failure – however unlikely – a good plan is to have some back-up buoyancy or a structure plan that includes some potentially helpful suggestions.
Here are a couple of tactics that may help you if the inflation hose and your wing become separate entities while you are faced with a long ascent between you and a cup of hot chocolate back on the surface.
My council would be to forget trying the “swim up balanced kit” technique. By all means work on the principal of wearing a “balanced kit,” but understand that a long staged-decompression ascent is not something you want to undertake as a continuous swim.
If there is structure nearby – a wall, shelf, wreck whatever — use it to stabilize yourself. Grab it, get yourself sorted out, “talk” the situation through with your buddy and try to relax. Unless your wing failure was accompanied by a huge loss of gas from your cylinder, you have something to breathe while you think. Relax and work out your options. If there is no structure, grab your buddy and use them as a stabilizer. It’s surprisingly simple to hang onto a buddy’s harness and let them add a little additional gas to their wing to support the two of you. But it does require a little practice!
Let’s assume you are wearing a drysuit. Add a little gas to it to offset gravity a little. You may be lucky and your suit may be all the help you need. Keep your buddy or buddies close, and start your ascent. Good luck and let’s meet up for a coffee sometime… but chances are that your suit may not overcome gravity’s pull completely.
If there is an upline, make for it and use it. At this point it may be worth noting that a prussic loop can be useful place to hang from while you work on options. A prussic is simple to tie to an upline and can be used just as effectively as an ascender is used in rock climbing (their original application). I carry a length of 3mm equipment line tied in a long loop in my wetnotes for this reason.
Things should be golden with the combination of a solid upline, a drysuit and a prussic loop, plus the administrations of your buddy to help with stage deployment etc. as needed. But what if there is no upline.
This would be a good time to send a DSMB aloft. Actually, it may be prudent to deploy a DSMB even if there is an upline, depending on how your surface support has been briefed. With the exception of the very smallest, silliest “safety sausage,” a DSMB (a Delayed Surface Marker Buoy) should provide sufficient lift to support a diver in place of a wing. If you have the choice, you may prefer to hang from a line attached to a small cave or wreck reel rather than a spool in this situation, but either works just fine… and spools rarely jam or bird’s nest.
In several thousand dives, I have had one wing failure and one buddy have a complete failure. I have conducted a couple of test dives with the dump valve removed from my wing – just for the fun of it – but only one real-world failure. Therefore, the weight of logic and statistical evidence is on their side of the argument that states that this type of gear failure is highly unlikely. It really is, and chances are it will never happen to you at any time. However, next time you have a dive planned with your usual buddies at a site with a hard bottom within sensible distance of the surface, and you have nothing better to do, try this. Empty your wing completely and get yourself back to the surface using an alternative method. You will certainly learn something about yourself and possibly your buddy, and most likely you’ll have fun too.
Remember as well, it does not take much to contingency yourself out of the water, but with a little forward thinking, planning and practice, there is no need to.
Doppler's Tech Diving Blog 