How do I get there from here… Step one on the road to Technical Diving

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Here’s a very simple piece of advice if you’re being pressured — by your mates, your instructor, or a little voice inside your head — to sign up for a dive class. BEFORE wasting time and money on another course and its accompanying piece of plastic (or eCard): “GET A PLAN.”

Base that plan on what you want out of diving, and how much of your free time — and disposable income you want to dedicate to your plan.

Also, it will help motivate you if you work towards your goal with a buddy who has similar aspirations. Kinda like having a running mate who you can trust to ignore the rain and the wind, and to meet you at o-dark hundred on winter mornings to jog 10 k.

And finally, be realistic with your schedule. You will be doing yourself a disservice piling training sessions one on top of the other. PACE yourself. There’s no prize for the one who “finishes” first.

(Well, two things about that: there is no finish, at least none I can see. After more than 20 years teaching technical diving, I’m still learning; Secondly, you will grow more and become a better diver by punctuating your dive trips (read “experience gathering expeditions”) with targeted training sessions rather than the other way round. There is certainly no set ratio; everyone is different, but think about starting out by saying for every thousand dollars/pounds/Euros/shiny beads I spend on travel, I’ll put 200 in my training fund piggy bank.)

Okay, so here are ten tips to help you get your plan created:

  1. Have a long-term goal in mind. “I wanna dive the Empress of Ireland, the Bianca C, and the MS Mikhail Lermontov; I want to swim the Grand Traverse; I see my future-self on a rebreather at 100 metres taking samples for scientific research; My daughter and I have a trip to Truk Lagoon planned and I wanna be ready, etc.” All perfectly valid goals. Write yours down on a piece of paper and stick it on the fridge door.
  2. Create a budget for time and money. Quality training cost money. For many classes with a professional instructor, you should be planning to spend $250 – $350 per person, per day on average. Most classes, complex classes like cave or decompression or basic CCR, can last five or six days. By all means research your choices; get booked with someone you’re happy with, but don’t skimp on money or time.
  3. BEWARE of any operation/individual guaranteeing you’ll get certified. Technical certifications are earned not bought, who knows how you’ll do? There are no guarantees you’ll pass; but a good instructor will make sure your experience will be money well-spent.
  4. Create a timeline… with waypoint so your progress can be followed. You’ll need help with this. Ask advice. Then get a second or third opinion. The answers will tell you a lot about the instructors/operations/dive shops you ask!
  5. Think laterally when searching for help with training (your pathway might take you away from your local dive shop and towards an independent professional, it may take you to the next town or out of the country. So, THINK GLOBAL… it’s make you grow.
  6. Ask: Am I ready to have most of what I know about diving, challenged and modified?
  7. Am I willing to travel?
  8. Do I do well with constructive criticism? Technical instructors are trained and conditioned to pick bad habits apart. The process can be unsettling for a student with “issues.”
  9. Are you aware that going deeper, staying longer, breathing different gases, swimming in overhead environments all carry more personal risk of injury, death or worse?
  10. And finally, you need to understand and appreciate that some forms of diving are addictive. They will take over your life. Are you ready for that?

 

Good luck and “Dive Safe!”

Stage-bottle logic

OTHREE THERMAL PROTECTION

There are different schools of thought about the “best” way to manage gas volume when cave diving with stage bottles.

The so-called traditional method is to treat the gas carried in stages, exactly as the primary gas supply: breathe one-third on the way in; one-third on the way out; and leave one-third for contingencies. If nothing hits the fan on a dive following this method, divers surface with stages, and primary cylinders each about one-third full.

Yet another option is “half + 15.” With this method, contingency gas for the stage is carried in the primary cylinders. This method requires a little more thought and arithmetic; but is considered by some to be the most conservative and best method when multi-staging. If everything goes smoothly when employing this method, divers surface with stages close to empty, but with all the contingency gas in their primary cylinders, which — with a single stage — translates into the primaries (twins or sidemount) being around half-full or more.

And finally there’s the seat-of-your-pants method which like half + 15, allows around half the volume of the stage bottle to be breathed, but critically, unlike half + 15, does NOT preserve any additional contingency gas in one’s primary cylinders. Provided nothing goes awry, divers using this “technique” surface with empty stages and primary cylinders with about one-third remaining. You don’t have to have a phD. in risk assessment to realize this is the most “liberal” way to dive stages; if anything dramatic happens, it can mean that divers do not surface at all.

But let’s leave discussion on the pros and cons of each method as the topic for a later blog post. Let’s focus instead on an error we should avoid when diving with stages in a cave regardless of which gas management rule we follow. That error is dropping a stage immediately its turn pressure has been reached.

It seems to be a more logical, more conservative, and therefore better practice to carry the stage and it’s extra gas a little further into the penetration.

Let’s look at a couple of disaster scenarios, and see why the habit of carry stage bottles a little deeper tends to be the better option.

Two divers (the ubiquitous Diver A and Diver B) have planned a stage cave dive. For the sake of simplicity, each is using the same size primary cylinders and each has the same sized aluminum stage bottle. Each has identical consumption, and fill pressures in all cylinders are identical. (An unlikely situation, but convenient for our purposes!)

Also, to forego any confusion over bar/litres or PSI/cubic feet, let’s consider the starting pressure in the primary bottles as 3P; and in the single stages as 3S. Our divers, A and B opt to dive following the Rule of Thirds in both primary and stage bottles.

OK, scenario one: Our divers begin their dive and, conventionally, breathe from their identical stages to start their dive. After a pressure drop of 1S, they drop their stages… each has 2S of gas remaining .

They swim on breathing primary gas. They each consume 1P of primary gas and signal “turn the dive.” At precisely this moment, Murphy joins their dive, and Diver A has a massive problem with his primary gas supply. He signals his buddy, and they share gas. Now Diver A and Diver B are breathing from Diver B’s 2P volume of gas.

If things go well — no entanglement, no slowing down because of restrictions, no elevated breathing rates, no taking a wrong turn in the confusion, and no arguments over navigation — they make it back to their stages with zero pressure in Diver B’s primary cylinders.

They grab their stages, and spend the rest of their exit thinking about how close a call they just had. They each surface with 1S pressure of gas in their stages, but zero in their primaries.

OK, scenario two is similar: But in this case Diver A and B when they have consumed 1S of the gas in their stages, switch to their primary gas, and opt to carry their stages a five or six minutes, or more, further into the cave before dropping them.

At the same point in the dive — just after the turn — Diver A suffers the same disaster, and has nothing to breathe. So, both exit breathing from Diver B’s 2P volume of gas; however, in this case, they reach their stages a few minutes earlier than in scenario one. There is gas in Diver B’s primary cylinders when they pick up their stages and continue their exit, during which they give thanks that they carried their stages further into the cave.

They surface with less than 1S of gas in each stage having perfectly justifiably used some of the reserve contingency gas in those stages to exit calmly. Diver B has some gas in her primaries; and, as in scenario one, Diver A’s cylinders are still empty.

Now we might argue the likelihood of the type of complete gas loss Diver A suffered in both scenarios one and two as remote… highly rare, probably impossible. But what cannot be disputed is that in scenario two, by carrying their stages for just a few extra minutes during their swim in, they had contingency gas placed in a better place than in scenario one.

We can debate how best to manage contingency gas volumes in stages (there may be benefits to each method), but in most cases it seems a better, more logical option to think before you drop; and wait.

Dive Safe!

Double Arrows… what do they mean exactly?

OTHREE DRYSUITS

Cave divers have a secret code… well, according to a non-cave-diving buddy we do. And perhaps she’s right; we do have a few odd hand-signals that are specific to cave diving.

What I did not mention to her when explaining the peculiarities of “ I’m Stuck,” “Changing Second Stages,” “Tangled in Line,” and “Okay buddy, I’ll help yer, but you’re gonna owe me…” was that some of the basic signs we take for granted in North America, are not universal in every cave-diving community.

Double arrows indicating proximity to a jump / side passage is a good example. (See the photo below.) Outside of North Florida, this may or may not signal what it does here: time to tie in a jump spool, fix attendance cookies to the gold line, and “Let’s go roaming!”

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What’s perhaps more baffling is that even in the North American cave diving community, there’s a general misunderstanding about what exactly is meant by another set of double arrows.

The picture below shows two directional arrows pointing in opposite directions. Similar but with a very significant difference… well different certainly… but how!?

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Until recently, I thought it generally accepted that this particular configuration indicated the mid-point between two “Ends of Line.” But during the past month, diving various caves but none separated from another by more than a two-hour drive, I heard it referred several times as indicating a “Safe exit in either direction” or “The halfway point between two exits.”

While it’s a fact that an end of line — a break in the main line — is usually where the overhead has a hole in it and daylight streams into the blackness of the cave proper, that is absolutely NOT the same thing as a safe exit; and the difference is more than a question of semantics, with the potential for a bad day ahead for assuming it is.

So, lets think about why this is.

A cave diving team, unless one of them’s clairvoyant, can only be sure of one safe exit: the one they came in by. Everything else is a mystery, and in truth, in a few cases there’s no absolute guarantee that when they get back to the hole they came in by, it’ll still be passable. Perhaps the only sure bet is large, open caverns like the entrance to Jackson Blue Springs in Jackson County, on Florida’s panhandle.

Caves, and especially sinkholes, have a dynamic nature. A sinkhole that a diver could climb in and out of yesterday, may have suffered a mini-landslide overnight making it impassible today. A tree providing shade last week, may have had its root system undercut by yesterday morning’s downpour, and is now sitting in the sinkhole like Aunt Zenia’s potted aspidistra: short of digging out, there is simply no exit now. A rock may have fallen from the ceiling a few feet from the sinkhole blocking access with an immovable chunk of limestone and 40-million-year-old fossils.

So, that’s why it’s a little risky to assume the mid-point arrows indicate anything other than equal distance between two ends of the main line, and nothing more… at least that’s the case in North Florida.