Air today, trimix tomorrow
Extended-range diving means taking air and nitrox to its limits before moving on to trimix. Last year our training correspondent Chris Boardman sampled PADIs extended-range course - now he turns his attention to TDIs well-established equivalent

LYING ON MY BACK UNDER 5M OF RED SEA IN TOTAL DARKNESS (thanks to the blacked-out mask I was wearing), I had to make a conscious effort to regulate the amount of salt water going up my nose (thanks to the holes cut into the bottom of the mask).
The object was to de-kit, including stage cylinders, and re-kit, with touch being the only sensory input. I had completed the first part and was floating in front of my equipment when the regulator from which I was breathing free-flowed.
The exercise was one of about 14 in Leigh Cunninghams skills circuit. Why was I doing it Because I had completed PADI/DSATs Tec Deep Diver training, and wanted to compare this technical offering with a more established course. I also wanted to spend more time in Egypt.
Technical Diving International came to the rescue with its Extended Range course. My instructor remained Master Leigh from Ocean College, now back on more familiar ground teaching TDI.
Some of you might remember my original description of Leigh, as a tec fanatic. Since then, I have also heard him described as being like Catweasle - a genius but a little mad. This description certainly fits when you see Leigh dance, but perhaps thats another story.
The depth limit adopted by TDI on the four-day course is 55m as opposed to PADIs 50m, with a recommendation for divers not to exceed 66m using air on any dive thereafter. This is the point at which the oxygen content of air reaches a partial pressure of 1.6, widely recommended as the limit for O2 exposure.
Here, the similarities between the two courses ended. The TDI course was much more a matter of imparting valuable information from one experienced diver to another, as opposed to PADIs student-teacher relationship.
Leigh told me that, apart from the written exam, the content and passing criteria for the course were left largely to the individual teaching it. Thats why, if youre taking the TDI route, it is critical that you get the right instructor.
I was joined on the course by two other scuba instructors. One was Steve Turly from Ocean College, who had been teaching for more than 10 years, the other an old friend of Leighs, recently out of the army, based further down the coast and known as Shniffer.
Having come straight from the PADI Tec Deep course, I had a bit of an advantage over Steve and Shniff. I had a good idea of what was coming and had practised a lot of the activities, such as dropping reels at critical moments, choking on inhaled sea water and forgetting basic pieces of information learned on my Open Water course.

Day 1: The skills circuit
You cant know how well you will perform under stress until you encounter it. Day one was designed to let us find out.
This dive, at nearly three hours, was the longest I had ever done. By the end of it there were still one or two exercises uncompleted, but in water temperatures exceeding 27ÂC, this was no great hardship.
There were similarities between the skills circuit here and the one I had done before, but also some notable additions, such as use of a blacked-out mask and a 40m (I kid you not) no-equipment swim along an L-shaped route to retrieve an object, before returning to our gear and that oh, so lovely gas.
There was a lot of reel work too, including a 20m swim down a simulated cave line, with blacked-out mask and no regulator, to a stage cylinder tied off at the other end. This had to be orientated and turned on before we could breathe off it.
Without the benefit of vision and with an increasing sense of urgency, both my colleagues mistook the A-clamp yoke knob for the cylinder valve and started removing the regulator from the cylinder by mistake! Fortunately both managed to correct the problem quickly and complete the exercise.
All the skills were similarly challenging in their content but, as in the PADI course, youll be pleased to know that there was always a regulator (yes, turned on) available to a candidate unable to complete the task.
The point of the circuit is to show divers that their physical limits are much further away than they realise, and to train them to react appropriately under stress. Should a diver be unable to complete a task, he would not necessarily fail the course.
It was another very intense but instructive dive. Leigh preferred to call it fun-filled.

DAY 2: Deco-diving
TDI expects, in fact demands, that all candidates be good divers before even starting the course. So it was not surprising that we went straight into decompression diving.
Our first dive was to a planned maximum of 52m, where we would perform some simple tasks before ascending using nitrox 40 and 60 for decompression. Everyone was a little shabby in the execution of the procedures, but despite the usual surprises, such as sudden mask loss and regulators free-flowing along the way, it went OK.
Towards the end of our half-hour deco at 6m, Leigh showed us how to breathe off a cylinder without a regulator attached, one of the skills we had failed to get round to the previous day. We then had to do the same while holding our stop depth accurately for at least a minute. It was easier than it sounds.
This is not a technique one would expect to use in an emergency, but the rationale behind practising it was sound. Simply knowing that after plan B you have the potential of plans C to F available for getting out of trouble is tremendously valuable psychologically. And when you are in an alien environment, psychology is very important.

DAYS 3 & 4: Going deeper
The next two dives were more of the same, but the depth was increased to the course limit of 55m.
After dive three, while still on the boat coming back from the dive site, we all took the final exam, a combination of multiple-choice questions and dive-planning exercises.
The next day, reinforcing the disciplined approach applied to these and indeed all dives, Leigh informed us that if anyone exceeded the planned bottom depth by as much as 10cm we would have to repeat the dive. This also went for breaking decompression ceilings.
Although diving in a team, we were instructed to start approaching every dive as if we were doing it solo; self-sufficient in everything and all life-support equipment at least duplicated. The only thing for which you looked to the team was a back-up brain. I started to appreciate the arguments for solo diving.
The dive over, and in the final minutes of our 6m stop, Leigh produced the slate bearing the words Congratulations ER Diver!

The following day we made another trip to Thomas Canyon for a 66m dive - the only non-training dive of the two-week trip.
I would have serious reservations about approaching this depth in UK waters using air, but in the near-perfect conditions in the Red Sea - virtually no current, infinite viz and 28ÂC water - we were all comfortable that this was acceptable.
We descended at the chimney end of the canyon, continuing past the coral arches to a narrow passageway about 15m long and passable in single file at 64-66m. As we swam slowly along the dark passage, the presence of narcosis was very noticeable, prompting me to do a quick equipment and gas check.
We exited into the main canyon in incredible cathedral-like conditions, and felt privileged to be enjoying a sight that not many people experience. The bottom was only just visible, and a trimix course was looking more tempting by the minute.
We ascended to 60m and continued along the canyon until we reached the boulder choke, which signified that it was time to go up. With some regret we paired up and prepared to leave.

If you want to get into technical diving and go the full TDI route, you need to take its Advanced Nitrox and Decompression Procedures courses before being eligible to do Extended Range.
This would make the cost and time involved comparable to the 8-10-day PADI/DSAT TecRec course for a similar level of training, but you would be able to split your training into smaller, more manageable chunks of time.
Luckily for me, the PADI course is already being recognised by TDI as Decompression Procedures and a bit, which is what enabled me to go straight into Extended Range.
The course was supported by a rather bland-looking manual that appeared to be fresh off the nearest photocopier - which it wasnt, as it was an original TDI product. It covered all the salient points and spent a considerable time covering human physiology and the effects of pressure on it.
Despite the visual presentation, it was well-written and very easy to understand, with knowledge reviews following each chapter. TDIs club-like training stance does give an awful lot of responsibility to the instructor to define what needs to be taught and what constitutes mastery of the skills.
With the right instructor this system works fine, but it works only because TDI is relatively small, and can vet each instructor that it passes by means of a peer-review system.
If and when this organisation grows, it will have to put more definable checks and balances in place. One rotten apple slipping through the vetting process could severely damage all that this organisation has achieved.
As I was taught both the PADI Tec Deep Diver and TDI Extended Range courses by the same instructor, it will come as no great surprise that I found my instruction on both courses more than adequate. Both methods conveyed the necessary information to me.
However, with TDI this was due more to the quality of the instructor than the material he had to teach. Because of the more clearly definable standards put in place by PADI, I would probably recommend its Tec Deep Diver course to a would-be-tekkie friend.

  • Chris Boardman dived with the TDI Middle East facility at Ocean College in Sharm el Sheikh (Explorers Tours 01753 682 660). For TDI/SDI course details call 01752 872 413.

  • Master
    Master Leigh Cunningham, Chris Boardman and another student, Doozer, after completing the skills circuit
    Getting used to carrying out tasks by feel alone - its important to turn the correct knob!
    A student in blacked-out mask and no regulator traces a 25m line to find a stage cylinder
    Regulator failures occur while line-laying without a mask - will he hang on to his reel while shutting down
    Reaching the gas which tastes all the sweeter after a period of deprivation

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