AFTER ALMOST THREE HOURS under water, the divers surface silently behind the boat and slowly fin to the ladder, where the crew is waiting to relieve them of the torpedo-like propulsion vehicles they’re towing. They unclip unused cylinders slung to their harness, and hand them up carefully.
Back on deck they close the mouthpieces integral to their full-face masks and check the twin monitoring devices strapped to their forearms before shucking off their shell-clad electronic life-support devices and laying them down gently.
The atmosphere is calm. There is no whooping, hollering or backslapping, even though they have just accomplished the sort of dive that would have been impossible a couple of decades ago.
Tomorrow they will carry out a similar but deeper dive. On Monday they will be back sitting behind desks wearing a different kind of dark suit.
These are not professionals, military divers or explorers; they are just two guys out of the city on a long weekend break, indulging themselves in their hobby.
Their chosen sport is technical diving; extreme scuba-diving performed with a high degree of preparation and precision.

A LITTLE HISTORY
The term “technical diving” was coined in 1991 by Aquacorps magazine founder Michael Menduno to bring under one banner the activities of a number of groups of divers up and down the east coast of the USA.
They were all using technology, ideas, equipment and decompression tables that had formerly been the province only of professional military or commercial divers to go safely beyond the bounds of normal sport-diving to explore caves and deep shipwrecks.
A community was formed, specialised training agencies were set up, procedures were debated, information was shared and news spread quickly. People came flocking from all over the world to acquire the skills and knowledge that would enable them to exceed the sport’s commonly accepted limits safely.
The diving-industry establishment was outraged. Many people forecast disaster, and there were campaigns to ban this “dangerous” new trend.
But the lure of hitherto-unimagined opportunities was too strong, and divers continued to queue up to acquire the necessary equipment and training.
Eventually, the industry gave in to popular demand. Now most of the mainstream diver-training agencies offer technical diving courses.
But how do you know if you’re the sort of person who would make a good technical diver? How do you choose a course, what equipment do you need and what other things should you consider?

A TECHNICAL MINDSET
The popular (and erroneous) image of a technical diver is an adrenaline-crazed individual, dressed from head to toe in black, foolhardily festooned with the contents of a small dive-shop, launching himself into the depths without a thought for his own safety.
This image is reinforced by the common practice of defining technical diving in terms of the nature of the dive or the equipment used – a dive deeper than 40m, using gases other than air, inside an overhead environment such as a cave or shipwreck, using multiple cylinders or rebreathers.
However, when a diver armed with standard scuba-gear plummets below 40m or swims down the corridor of a ship, that doesn’t make his dive “technical.” When a diver uses a rebreather, he doesn’t immediately become a technical diver.
The true definition of technical diving owes far more to the attitude and state of mind of the diver than the particulars of the dive. A technical approach to a dive involves analysis of the risks involved, the amount of gas required and the best equipment and gases to use.
It also involves consideration of potentially life-threatening events that might occur on the dive, and an assessment of the skills and back-up equipment that the diver might need to deploy to survive any such event.

MOTIVATION
Most of the early proponents were explorers driven to go further: to set records, visit virgin shipwrecks, solve maritime mysteries, penetrate flooded cave systems, learn more about the sea and record and research marine life.
Some of those who have followed them share similar ambitions, but there are also many who are simply motivated by knowledge and skill development, a desire to improve their level of performance, to master their sport, to become a better diver.
Contrary to common misconception, very few people are brought into technical diving by the quest for a thrill or adrenaline rush. After all, rather than court danger, the whole ethos of the sport is to counter risk by the application of planning, training and technology.
Most technical divers are thoughtful people who are attentive to detail, sometimes to an obsessive degree.
Is this you? Would you make a good technical diver? It isn’t always wise to generalise but there would seem to be some essential prerequisites:

1. EXPERIENCE
It’s not the card you hold or the number of dives you have logged that counts, but the nature of the diving you have done. Ideally, you need to have experienced a variety of environments and water conditions.
2. SELF-RELIANCE
In the technical world, divers perform as independent parts of a mutually supporting team. You are responsible for your own dive.
3. COMPETENCE
You need to have mastered basic scuba-diving skills before progressing to this level. You should be able to control your buoyancy instinctively and have no problem being under water with no mask on. A good grasp of decompression theory is useful.
4. SELF-DISCIPLINE
You must be able to stick to a dive-plan. While standard no-decompression single cylinder diving offers guidelines to follow, technical diving has strict rules based on physiological and physical limits – rules on which your life depends.
5. METICULOUSNESS
If you are the type of diver who regularly jumps in without securing your BC to the cylinder or turning your air on, then technical diving may not be for you.
Ask the people with whom you dive.
Do they privately consider you an accident waiting to happen?
6. FITNESS
You should be mentally and physically fit. Technical divers carry more gear, swim further and stay under water longer.
7. ACCEPTANCE OF RISK
Technical diving involves a higher level of risk. Are you and your family prepared to accept this?
8. FINANCIAL HEALTH
Technical diving requires a substantial investment in training, equipment and travel. There are no short cuts. Cheap training at this level is likely to be inadequate training.

OPEN OR CLOSED?
If you choose the open-circuit route to technical diving, you develop the skills and techniques you already have. Closed-circuit diving, however, is a new world. When you start diving a rebreather, it’s best to adopt the that you are learning to dive all over again, and keeping your mind entirely open to new ways of thinking and doing things.
If you’re hoping to graduate eventually to very deep diving using mixes heavy on helium, then closed circuit really is the way to go, because the quantities of helium required for very deep open-circuit diving make it extremely expensive.
Yes, rebreathers are expensive to buy, but once you become a deep trimix CCR diver, you earn back your investment very quickly, because your helium cost is far, far lower than it would be if you did the dives on open circuit. In Europe these days, it is rare to see open-circuit divers on the deep-diving boats.
You’re going to have to buy more gear, even if you don’t choose the closed-circuit route. You will need two good regulators for your back-gas, and two more for your decompression gases.
Other essentials include a harness and wing for your double cylinders, submersible marker buoys, reels, cutting tools, slates, waterproof tables, a multi-gas-capable computer and a dive-timer.

A LITTLE ADVICE
Don’t buy without expert advice. Technical diving is challenging and rewarding and it can take you to places on our planet seen first-hand by very few. But you have a lot to learn before you get there, so prepare for a lengthy journey.
There are several levels of training to pass through, and the courses only introduce you to the concepts and give you a little practice. So take it slowly and don’t let anyone rush you.
Do plenty of diving between levels to assimilate the new techniques and acquire expertise before moving on to the next level.

Read more from Simon Pridmore in:
Scuba Confidential – An Insider’s Guide to Becoming a Better Diver
Scuba Professional – Insights into Sport Diver Training & Operations
Scuba Fundamentals – Start Diving the Right Way

All are available on Amazon in a variety of formats.