The Six Basic Skills: Number Two, Situational Awareness

Situational AwarenessOf all six basic skills, Situational Awareness (SA) is my favorite skill to teach and coach. And, like Breathing, it is one that is virtually ignored in mainstream diver education programs, yet it is without argument a critical part of safe diving at any level; particularly in technical diving.

Put briefly, SA is the chess-player’s skill but applied in an environment where checkmate can result in real physical harm, and not just a wooden game piece being knocked over sideways.

SA has been a core concept in high-stress operating environments, such as the military and aviation, for many years. SA skills support the ability of individuals operating in this type of environment to handle complex and rapidly changing situations in which informed decisions need to be made under tight time constraints.

The simplest definition I’ve found is that SA is being aware of what is happening around you and understanding how information, events, and your own actions will impact your goals and objectives, both now and in the near future. Sounds exactly suited to the underwater realm to me.

definition of Situational Awareness

The most authoritative voice in the study and application of SA is Mica Endsley, and I would suggest you find a copy of her white-paper: Toward a Theory of Situation Awareness in Dynamic Systems if you are interested in digging deeper into SA theory and practice. But it’s not required reading. As Endsley says, prehistoric humans probably had an innate understanding of SA in order to survive so the basics are hardwired into us all. We just have to work at pulling the skill out from behind all the civilized creature-comfort complacency that prevents us from bringing it into the game at playtime.

Endsley defines SA as, “the perception of elements in the environment within a volume of time and space, the comprehension of their meaning and the projection of their status in the near future.” And she breaks SA capability into three levels:

1/ Perception – of cues and stimulus from the environment
2/ Comprehension – involving the integration of information to facilitate relevance determination and sense-making
3/ Projection – the ability to forecast future situation events and dynamics

In addition, Endsley highlights the importance of temporal factors to SA, for example in understanding:

    a/ how much time is available until some event occurs or some action must be taken
    b/ the rate at which information is changing currently to help project future state

Divers need to be on top of all three levels, and are required to make decisions in an environment where time is always in short supply.

Situational Awareness DiagramDeveloping SA, and being “good at it” is important, and a learned skill just like playing chess. As divers, we can we improve our SA through a few very simple techniques.

1/ Divide the dive into manageable segments to limit task loading
2/ Set way points and do not become distracted
3/ Track actual progress against dive plan
4/ Make allowances for Murphy
5/ Make adjustments within the constructs of the dive plan and only within the dive plan
6/ Identify problems early. This is key. If something appears to be going off the rails, it probably is. Do not ignore it!
7/ React immediately or before! Seriously, act to correct a minor infraction before it grows into a problem.

As a diver’s SA becomes more attuned, he notices more about his surroundings and situation.

Typically, a novice diver has a limited awareness of self, some awareness of equipment, but can easily loose track of his buddy and be taken off guard by changes in his surroundings. Just by being in the water, he is task-loaded and his SA drops off to zero. If you are going to function as a good technical diver, your SA has to be at a seven or eight at least! Be aware of yourself; how you feel and how comfortable you are. Be aware of your kit. Does it feel right and is it functioning correctly? How about your buddies? What’s happening with them; does everything look as it should? And finally, your surroundings; are they what you planned for? Is there anything out of place or not as you expected?

Situational Awareness really boils down to being alert and cautious. For example, a technical diver only looks at his SPG to confirm how much gas is left in his cylinders; elapsed time, and his work level will already have informed him what reading to expect. Situational Awareness also informs a good diver if a team member is uncomfortable or stressed by reading his body language and small hints like breathing rate (assuming open circuit of course). It will also allow him to notice that a team member has a piece of kit out of place before that team member does.

LACK OF SA is the most common reason for a student at this level to fail his course!


Technical Diver's Credo

Something worth remembering. Please write this down. Any diver can thumb any dive for any reason… no questions asked.

During our time together, if you feel uncomfortable, stressed or feel that things are not going as planned during a dive and want out, do not hesitate to CALL THE DIVE.

There are a number of mistakes a diver can make at this level. One of the most SERIOUS is to put-off calling a dive.


Some random thoughts on teaching buoyancy… one of the six skills

I have to be a bit pedantic here… in the real world outside of diving where there exists some semblance of respect for the constructs of everyday science, there is a place where there is no neutral, positive or negative buoyancy. It is a happy place and I like it there.

Neutral, Negative, Positive. These are outcomes and not states of buoyancy. I know it is a hard habit for divers to break – like referring to the Gas Laws as physics when they belong in the realm of chemistry – but I would suggest at this level you should understand the distinction.

Things float, things sink, things maintain their position in the water column: Which of these outcomes corresponds to our state as a diver, depends on the balance between gravity and buoyancy.

It will help us understand this skill more completely, I believe, if we first understand that balance is the variable while gravity and buoyancy are the constants.

So just to recap, there is no such thing as negative buoyancy; that is like saying a color is whitish black or a cup of coffee is Hot Cold.

Positive buoyancy is redundant term at best. But it could also mean that a buoyant force is optimistic; which is just plain wrong.

Neutral buoyancy assumes some all-powerful entity has suspended the Laws of Physics.

Any questions?

Presentation to 41st NACD* Conference. November 21st 2009

Forgive me for straying somewhat from the agenda, but it seems the diving community needs your help; needs help from us all.

As many of you know, there appears to be a general misunderstanding among the general diving public about standards, protocols, guidelines, rules. Call it what you will, but something is just not squared away with the tech diving community; and people are getting themselves killed because of it.

Every one of us knows that diving is dangerous. And we know that anyone telling us otherwise is either delusional, completely ignorant in the art of risk assessment; or they are lying.

Technical diving, what we are most interested in, is extremely dangerous; perhaps an order of magnitude more risky than common or garden sport diving. But we render the risks manageable by simply following some really basic rules. These boil down to staying within the limits of our training, our skills and our experience; making a dive plan that takes into account the lessons learned from accident analysis; PLUS we adapt our plan to account for the actual environmental conditions we find at the site on game day; and, of course, we stick to our plan.

Risk management is even better assured by resisting any temptation to push our comfort zone or that of our companions. And we are well armed against the wiles of Murphy if we are prepared to react creatively when the dynamic nature of diving presents us with “real-time” challenges without warning.

In any high-risk activity where we want to weigh the odds of a favorable outcome, the normal path is to follow what’s called Best Practices or Best Practice Behavior. It’s really just a label we stick on a process that leads us along the, statistically speaking, safest pathway through a series of conditions that present threat; either physical, societal, financial or psychological.

However, there are few guarantees and every year divers die.

In rare cases, divers die even though they have followed best practices. They do everything according to the book, but die regardless. The issues in very many of these incidents are truly accidental; often an underlying unknown health problem; and heart problems seem to top that list.

But in the great majority of cases, people die as a direct result of NOT following best practices.

In some cases, their mistakes or the mistakes of their buddy or instructor were errors of omission. What I mean by this is that they forgot to do something important or maybe were unaware that conditions, equipment, personal needs or a combination of all three were going to demand something they could not provide. These events are sad.

At the other end of the scale of culpability, and a factor in the majority of diver deaths, are mistakes that are errors of commission; which in this context I take to be deliberately refusing to follow what they knew at the onset of their dive was best practice. They knowingly did something negligent and these events are tragic in the truest sense of the word because they are avoidable; totally, 100 percent avoidable.

Now, all this is pretty obvious to you and me, but in the past couple of years, our community (the technical diving community at large) has suffered several shock looses and almost every one appears to have been a direct result of divers trying to pull off dives using the wrong gas, wrong kit, having inadequate skills, or inappropriate training. In at least one case — a young man diving air to 75 metres (about 230 feet), well beyond the most extreme limits for that gas in consideration of narcosis and oxygen toxicity — a strong influence would appear to have been pressure from an employer slash instructor; in other words, someone they looked up to.

When invited to come down here and talk to you folks today, I jumped at the chance because I like cave country, I like cave diving, and apart from a bias against Alabama in favor of the Gators, I feel comfortable among cave divers.

My intention was to give a light-hearted presentation pointing out some of the influences that North Florida cave divers have had on the wreck diving community and underline the way we wreck divers have evolved the basic cave diving kit and skill sets to fit a very different environment. We are still going to look at that but from a viewpoint influenced by several recent deaths. None of us knows much about any of these incidents, but there is a common theme in at least almost every case; Lack of Training. Specifically here in North Florida, divers who had no cave training, dying in caves; what a sordid cliché that is, and how sad it’s still happening.

Of course it begs the questions: what can be learned from the misfortune of others, and how can you and I help prevent, by example or influence, others from repeating the same mistakes?

Let’s start with a few declarative statements.

Number one: Wreck diving is very different to cave diving. They are cousins, siblings even, but certainly not identical twins.

Number two: If we accept number one, it follows that the skills required for diving wrecks and diving in caves are NOT interchangeable. The skills have the same names but their deployment is different because the environment is different.

As a result of these two issues, it is NOT possible to train cave divers in wrecks nor can one train wreck divers in caves. To attempt one or the other is wrong and it is dangerous. Since technical diving is risky to begin with, sending the wrong message to the people we train in either of these activities just throws a wrench into the whole risk assessment / risk management exercise.

OK, let me add one more statement to those two. Without simulating or demonstrating the specific risks associated with a special environment – such as a cave – those risks do not exist for the student. In other words, taking a student into any overhead environment OUTSIDE of a course specific to that environment, be it cave or wreck, sends the wrong message. As mentioned, the risks do not exist unless they are explained and outlined with the big black magic marker of demonstration, guidance, performance, feedback and repetition.

OK, let’s start with some history, because if we go back to the start, we may get a better idea where the confusion comes from; and why some people think wrecks, caves and deep open water are similar.

A generation ago, when technical diving was coming out of the closet and before it became a convention, there really was only one place to go to get serious training. And that was Florida. Cave diving was and still is as far as I am concerned the original and purest form of technical diving. If you wanted to become a better wreck diver, and you wanted to learn techniques to make it so, you made your way to High Springs and signed up for a cavern/cave class, because organizations such as the NACD were the only ones offering an alternative to mainstream sport diver education.

Without doubt, because of this simple slice of history, almost everything that is the norm among technical divers around the world today, from Sydney Harbor to Seattle owes a serious debt to Florida Cavers. The classic back mounted rig; backplate, wing, doubles, long hose et al, had its genesis here in North Florida. Today, for some mystifying reason, this rig gets called DIR, Hogarthian, DW2, and god knows what else… but you and I both know that it is just standard North Florida Cave Diving Kit, and if it were not for the malleability of the road signs used by the Department of Highways, and Greg Flannigan‘s ingenuity, we’d all be diving poodle jackets.

The same is true of side-mount diving. Wreck divers are turning more and more to side-mount configuration for open-circuit wreck diving. In doing so, they are copying or borrowing from the kit configuration cave divers have been using for at least a couple of decades.

The connection is there. Cave divers and cave training agencies wrote the screenplay for wreck diving techniques and training. And so, if they are siblings, then cave diving is the older sister.

But over time things have evolved. Driven by a void or need within the wreck-diving community, technical instructors and training agencies have developed specialized technical wreck or advanced wreck programs. The starting point may have been the NACD cavern course but the program now has morphed into something more appropriate for the wreck environment and with attention being paid to skills that are not required in cave and cavern diving.

We do not have time to drill down into the nuts and bolts of each course and do a line item comparison, but we do have time to think about some major differences. So let’s look at them to justify our statement that the two types of diving are not the SAME.

Here is a partial listing of the skills tested during a TDI or NACD cavern and Intro to Cave courses.
• Gas Management
• Propulsion Techniques
• Deploy Guideline
• Lost Line
• Lost Buddy
• Air Share with Buddy in contact with line
• Air Share with Buddy blacked-out mask through restriction
• Light and Hand Signals
• Light Failure
• Problem Solving
Here is a partial listing of the skills for a TDI Advanced Wreck program.
• Gas Management
• Propulsion Techniques
• Deploy Guideline
• Lost Line
• Lost Buddy
• Air Share with Buddy in contact with line
• Air Share with Buddy blacked-out mask through restriction
• Light and Hand Signals
• Light Failure
• Problem Solving

They look the same don’t they; well, of course they are the same… But if we advocate and advise that caves and wrecks are different, how is that so? The answer is that it is in the application of the skills to the specific environment and not the skills themselves.

Gas Management: The Rule of Thirds is sacrosanct to cave divers and wreck divers but there are few wrecks offering several hundred metres of penetration; and so the rule’s application in wreck diving is far more like the Hub Plan used by CCR cave divers than the classic and simpler one third in, one third out used by OC cavers.

Propulsion Techniques: Wreck divers may have to employ a modified pull and glide to navigate narrow corridors inside a wreck where ANY fin movement is guaranteed to reduce visibility to zero in seconds. One other difference is that when a wreck diver kicks a wall by mistake is moves… it might even fall down. Anyhow, finning is NOT the default propulsion technique in “real” wrecks.

Guideline: Cave divers are warned about line traps. Cave divers can follow and usually do follow permanent lines for miles. Wrecks are one big line trap and a permanent line is the stuff of dreams. One might also consider that a continuous line to the surface covers a wreck diver’s need to be able to deploy a DSMB and decompress in blue water. In fact, that constitutes a required skill: hang off knotted line… keeping track of the knots to judge depth, with a blacked out mask, and counting breaths to track time.

Lost Line: Not a big issue when you carry the “permanent” line on a reel in your hand, but a required skill nevertheless for a wreck diver. However, more often than not, during their search for the lost line, students manage to get a manifold, spg, fin or something wrapped up in hanging cable… or their instructor’s simulation of hanging cable. Last time I audited a cave class, tying up the student was not part of the course work. It is in a wreck class. Another time for rodeo work is when students exit through a restriction with blacked out masks sharing air.

Communications, light failures and so on, are no different, but problem solving is. In a cave, the shortest route to fresh air is almost invariably back the way you came. In a wreck, the surface is closer but not necessarily easier to get to. And once there, getting out of the water may be a challenge.

Now if we stopped right now, some of you might leave here thinking, wow, wreck diving sure sounds tougher than cave diving. And in lots of ways, it is. But if things were that simple, how come we are not looking at a bunch of dead cave divers dying in wrecks instead of a bunch of wreck divers who are dying in caves. To be honest, I am able to turn up a constant and irreversible answer to that. But l have a theory…

Any of you who ski will have seen on the various ski runs leading from the top of the mountain back to the beer and nachos waiting at the bottom of the hill, a classification system indicating how difficult each trail is. A green run is the most straightforward; blue involves more slope and turns; a black diamond is technical and demands experience; a double black diamond is for experts and carries a real and present danger of injury or worse.

A skier can break his leg on a Bunny Hill (the simplest of green runs), but at least this classification system let’s punters like myself know which slopes to avoid on the morning of the first day of skiing after an eight month hiatus.

We avoid the black runs until we have our legs back under us.

There is no really well-established and universal “indication of risk” system in wreck diving or cave diving.

The powers that be do not post a series of Green, Blue or Black buoys above a wreck site for example. Perhaps one of the reasons for NOT posting colored indicators is that an errant fin kick, misplaced line wrap or simple quirk of fate can instantly turn a green dive into a black diamond. All experienced divers can all tell stories about a dive that started as a Green or a Blue but that went completely pear-shaped and immediately became a double black diamond.

But the point here is that many wreck dives and all open water dives offer the potential of a green or blue level dive. And in many cases, the journey to the wreck site is undertaken in a charter boat which gives some opportunity to restrict access to the dedicated black diamond sites.

So let me pose a proposition, and this flavors the magnitude of the request for help that I made earlier: I don’t think ANY CAVE DIVE can be classified as a Green dive. ALL cave dives, even a simple bimble in a place like Peacock, start out as a Black Diamond.

In addition, many cave dives on the other hand are “drive ups,” leaving them more open to abuse.

Touching the hull plates of the Empress or Ireland, counts as a dive, but swimming around the basin at Orange Grove is not a cave dive. If an open water diver wants to “give it a try?” he is totally committed and once beyond the grim reaper sign is participating in a Black Diamond level dive.

In addition, sites like Wayne’s World, the DiePolder system, and Eagles Nest are beyond double black… triple black perhaps. Yet we have divers with zero training, zero experience, who have no business being in there, diving in these spots… and not making it out

Now; who is at fault and how do we change things?

The easy out is to blame the agencies for not “controlling” the situation. But this is a rather naive take on the whole affair. It’s “Tooth Fairy Philosophy;” we can talk about it all we want… it’s still a myth, and believing in it will not make it any more likely to happen.

The agencies have an important role in things; they write standards, they enforce them – under the ‘strong recommendations’ of their insurance underwriters – and they set up a QA infrastructure for the network of men and women who teach under their banner. But agencies can’t work in a vacuum, they need feedback, information.

That leaves us. You and me; and to be completely clear on this, I have no foolproof plan. No guidelines for intervention. No killer argument or presentation of logic that is going to win people over when you bump into them getting ready to take their “Try It” dive in a site where they stand a good chance of topping themselves.

All I can suggest is that we work to educate and lead by example, and become more involved.

And as with any massive change or revolution, it begins with you. Each of us should ask ourselves the question are we diving the plan? Are we diving within the parameters of our experience and training?

As I recently wrote in partial jest, but the sentiment is real… All of you are now deputies, so get out there and kick ass… but before you do so, make sure YOU are without sin before you cast the first stone.

Thank You.

* National Association for Cave Diving

Diving: doing what works*

Hal Watts was warning divers to: Plan your dive: dive your plan, when a buoyancy control device was an empty bleach bottle with a loop of clothesline tied through the handle. Watts, one of the most colorful, popular and intelligent “pioneers” of technical diving, explained that the most dangerous thing about diving is divers themselves. “We do not belong down there and poor decisions and complacency lead to mistakes,” he says.

“The deeper one dives the more important it is to stick to a well-constructed plan because at depth, even a small mistake can quickly become a very serious accident.” And because of that, Watts has been stressing the need for a dive plan and the requirement to stick with it for decades.

Build your plan from the bottom up
The base structure of a good dive plan deals with the management of five constants: gas, gear, goals, team, and time. The surprise is that whether the dive is a ten-metre bimble on a sunny tropical reef, or a 100 metre wreck dive on a newly discovered shipwreck off Labrador, the basics of a dive plan are the same; the only changes are the details!

Gas management is always the first consideration, and begins with calculations for required volumes – for bottom gas and ascent gases (decompression gases). These volumes are workable quantities of gas based on a known personal surface air consumption (SAC) rate adjusted for depth, workload, environmental conditions, and various physical and mental stressors (dive factors). Armed with figures for projected gas consumption, final adjustments are made for contingencies such as lost gas or a longer ascent schedule, and variable consumption rates among all team members. The rule of thirds for bottom gas (based on the gas volume of the team member starting with the least amount of gas) and doubling ascent gas requirements are a good start and have become the gold standard among the open-circuit community doing staged decompression dives.

Under the gas management umbrella also comes planning for all dive operations to take place at depths where gases deliver acceptable partial pressures of nitrogen and oxygen. This matching process has to consider decompression obligations and narcosis; central nervous system toxicity for single dives and daily limits and – on multiday exposures – pulmonary or whole body oxygen loading.

In order to calculate decompression status divers have their choice of dozens of algorithms. Most teams get comfortable with one and stick with it. Frankly, there are more options for deco tables than watches in the Swatch catalog. A growing segment of the tech community opt to go with a dual-phase model such as one or the other flavor of VPM (Variable Permeability Model), but regardless of this detail, it is important to understand the parameters of the model chosen; most especially the behavior it assumes the diver adopts traveling between waypoints. Other must-knows are how to adjust the chosen algorithm for conservatism, and what changes it demands for contingencies such as longer bottom times, and lost decompression gas.

Narcosis is somewhat easier to plan around, but no less contentious. There are several things that influence narcotic loading besides nitrogen partial pressure and there’s a raft of information and opinions on that score. Cold, dark, current, fitness, work of breathing and a dozen more factors are thought to exacerbate narcosis, but a good place to start is to fix an acceptable partial pressure and work around it. There is no perfect solution but a lot of divers plan around a level somewhere between 3.0 – 3.2 bar. This equates to breathing air at about 30 metres (4 ata).

To help manage CNS and pulmonary oxygen loading, divers have the NOAA tables to fall back on. It’s worth noting that although the limits set out in these tables are almost universally adopted by the technical diving community, and have been interpolated via devices such as the ‘CNS Clock’ there is no real data to tell us that this works or is a valid strategy**.

With this is mind, a sensible tactic is to plan dives around VERY CONSERVATIVE oxygen levels especially on dives where carbon dioxide levels may be elevated due to high workloads, greater depth or shortened dwell times (CCR).

The secrets of gear management boil down to basic common sense moderated with experience. I am a fan of following the minimalist-oriented guidelines that suggest gear be: serviced (good working order); simple (no fancy do-dads); streamlined (zero danglies and configured to be as easy as possible to push through the water); standard (meaning that you and your partners have your kit arranged in a similar configuration that you know and can operate without stress and strain); and suitable (meaning every piece of gear that’s being taken for a swim is needed and unnecessary clutter is left behind).

These guidelines work equally well with open-circuit or closed-circuit gear; back-mounted cylinders or side-mounts, one cylinder or a half dozen; open water or overhead; hot or cold.

Typically, people carry too much tat with them. The habit of swimming with kit that will never be used unless the laws of physics suddenly change denotes laziness not preparedness. The problem is not just the additional weight that must be hauled around, and the corresponding inertia that has to be overcome even when kit is rendered weightless in water, but there are other issues.

Leaving bits and pieces of kit attached to a harness or crammed into pockets smacks of a complacent mindset. A classic example: backup lights. In some cases, these lay strapped to a diver’s harness for weeks without being tested or used or thought about. It’s as though they have become a sort of badge of belonging; to what I am unsure. OK, I know they don’t weigh much and there’s not a lot of inertia to overcome for a couple of flashlights, and they don’t really take up much real estate, but if the dive plan does not call for them, why on earth take them into the water?

Every dive should have an objective, a goal or a purpose; and every dive plan should reflect that objective and translate it into a set of waypoints that can be used to track progress towards completion. A 20-minute dip on a sheltered little reef within a stone’s throw of a beachfront bungalow in Bali by definition is most likely to have a pretty elementary objective and perhaps only a handful of waypoints; but that is not the case with technical dives.

There’s certainly no need to make an objective overly complicated. A reasonable goal for a dive is to see the inside of the wheelhouse on a sunken wreck, take a picture of the telegraph and get you and your buddies home safe and sound. The purpose of the dive could be to test a new strobe, and the objective to add another great underwater photograph to the ‘I love me’ wall in your home office. Easy enough but the whole thing becomes more manageable with a little road map to help get everyone to wonderland and back; those are the waypoints.

Waypoints can be physical landmarks along the way; predetermined marks on the clock; numbers on a depth gauge; pressure drops on an SPG; or a combination of all. Keeping track of waypoints helps everyone to join all the dots and keep up with the dive. Most importantly, it helps divers prepare for what comes next. That may be pulling out a reel, turning on a light, getting ready to switch gas; any one of a number of things. Waypoints help develop situational awareness (SA), and SA makes diving so much safer and more fun than diving with a series of events taking you constantly by surprise!

Always dive with a buddy. That’s something we have drummed into our heads from day one of open water class. What is often overlooked is giving us a glimpse inside the rulebook on how to make sure the buddy we dive with will help make the dive fun and safe rather than hell and dangerous.

Technical diving is sort of self-policing in this regard. Technical divers tend to limit their choice of dive buddy (or better yet buddies since the perfect sized dive team is three people and not two) to people who they know and whose mindset, training, experience and equipment is similar to their own.

The study of team dynamics glossed over, and the vagaries of human nature notwithstanding, the guidelines for putting a good dive team together and diving as a team are straightforward.

Everyone should be capable of doing the planned dive. The team should always stay together, but in the unlikely case of separation or a team member being incapacitated, the remaining member or members should have no problems completing the dives on their own. This is one reason to avoid so called ‘trust-me-dives.’

A trust-me-dive is usually preceded with the proviso: “I know you guys have never done this sort of thing before but I’ve done it a thousand times so just follow me.” It is the diving equivalent of the Darwinian Award Winner’s “Hey, hold my beer and watch this…” Needless to say, they are a bad idea no matter what; and of course are an exceptionally poor choice should anything happen to separate inexperienced team members from the “trust me I’ve done this before” guy.

On the positive side, the safer bet is to always plan a dive around the experience and comfort level of the least experienced diver, and in the water, this person takes on the role of dive leader. Leadership on the surface is usually the task of the most experienced diver, but in the water, this role is taken on by the least experienced. The logic is that the least experienced diver is unlikely to take the rest of the team into a spot that makes them uncomfortable, but will themselves feel comfortable pushing their personal comfort zone a little being in the company of “better” divers.

When a group of divers with comparable experience dive together, leadership duties fall to the “weakest” diver. Weakness in this case is not a pejorative but describes the diver who is carrying a ‘special’ burden. That burden may be a video camera and housing. They may have the least volume of gas, or they may have had a rotten night’s sleep the night before the dive or they may have thrown up on the boat traveling out to the dive site.

Equipment failures can change leadership. Anything that happens to a diver or a diver’s gear that signals “thumbing” the dive (aborting the dive and heading for home) automatically makes that diver the boss; and they lead the team out.

Team roles, the way those roles may changed because of changing circumstances or the dynamics of the dive, and the individual responsibilities of team members on the dive (and before and after) need to be included in a dive plan.

The final set of questions that a dive plan has to answer has to do with time; in effect, how long on the bottom and how long getting back to the surface. As mentioned earlier, there are library shelves filled with an assortment of decompression tables. The odd thing is that most work and lots are applicable to technical diving. And of course step one is actually picking one and then sticking with it.

With the advent of mainstream decompression diving and the whole technical diving thing pulling onto the freeway and joining the mainstream, there are scads of data about successful and unsuccessful ascents from all sorts of depths and durations using a variety of gases. Unfortunately, nobody seems to be collecting and collating it. This makes deciding which decompression model to use as much of a crap shoot as doing decompression itself.

The only constant is that decompression theory is mostly alchemy and very little is black and white; however, there are things a diver can do to beat down the risks to a generally acceptable level. All the old favorites from sports diving still apply; be hydrated, be rested, don’t push limits, control ascent speed, and so on. Technical divers can add to these: use the right gases, follow conservative profiles, and buy good health insurance.

There are no magic solutions or practices that can guarantee divers will not get bent and technical divers have to accept that an element of risk is always present, but there are a couple of things that may help.

First is to understand the way the table works. Most are built around a simple string of mathematical assumptions that attempt to model the vagaries of human physiology. Anyone looking with one eye sort of squinting and their head at a slight angle can look at a decompression schedule (regardless of its flavor) and see that the maths is producing a very distinct curve that describes changes to gas pressure over time. We don’t have to learn the differential calculus to get a handle on this, although it might help. It’s just a pattern. Furthermore, every ascent can be broken into five stages or waypoints and decompression tables dictate how fast or slow a diver can move between those waypoints.

For example, the distance (pressure change actually) between the maximum average depth of a dive and the point in the water column where a diver begins to offgas more than he ongasses, is a fixed point. It is influenced to some extent by the type of gas being used and the time spent on the bottom, but it is a real location. In truth the offgassing ceiling is more a mathematical construct than a physical need, but it is a very important waypoint on any decompression dive.

Knowing where it is in the water column offers a huge advantage to a diver because it tells him the point in his ascent where he will stop racking up decompression obligation and begin paying it off. It is a good strategy never to start a decompression dive without knowing where the offgassing ceiling or gas transition point is. Being armed with this little knowledge nugget is key to understanding the shape of the ascent curve and is the foundation of building a workable contingency decompression schedule in the event of a dive going totally pear-shaped.

Knowing where offgassing starts is also key to managing ascent because it is the point a diver needs to get to as swiftly as practical when the dive is finished. Not a big deal perhaps, but the most common mistake that I see among novice decompression divers is that their initial ascents are too slow and they travel too fast in the final stages.

I am a huge fan of having tables cut and sense-checked before a dive. After all, how can one work out the volume of decompression gases a dive requires without knowing how long the decompression is likely to be?

I am also a huge fan of taking notes before, during and after a dive. Like it or not, we are the guinea pigs in a vast, multi-user decompression experiment. What we do every time we go diving is validate a little piece of voodoo science. In a perfect world and as part of a real experiment, someone would take down the particulars; what we did, for how long, what we breathed and how we felt before, during and after (remembering that for some dives, decompression does not end for a day or so after we surface). These data are invaluable in helping to keep us safe. With notes kept up to date and available, a diver can make decisions about “TIME” that are actually informed by experience; and that is golden.

It is so easy…
I like surprises but not underwater and so I’ve cultivated the habit of trying to avoid them. Because of this, I cannot imagine diving without a good solid dive plan that manages each of the five constants: gas, gear, goals, team, and time. There are folks who think putting together a dive plan is too much of a bother, but the wonderful thing is that once you have developed a plan and used it a couple of times, it becomes part of the fabric of your diving. It becomes so easy that there is no excuse not to follow it. Of course, it helps if the plan is based on good sense because as well as saying “plan your dive: dive your plan,” Hal Watts also warned that a poorly thought out plan melts as soon as it gets wet.

* Doing What Works or DW2 is a catch phrase created by North Florida cave explorer Larry Green to describe a diving philosophy that seeks to keep divers safe and happy following a few simple rules; the most important of which is addressing the problems and challenges of technical diving with an open mind

** Bill Hamilton Presentation given at DAN Technical Diving Conference, Raleigh NC 2008