I'm trying to arrive at a "definition" that clearly separates the person from the dive. The focus is also today, not what it might have been 20-30-40 years ago, or what it might be in the future.
The Dive (i.e., the activity...not the person doing it)
Certain dives definitely require solid technical training and equipment, others certainly do not. Exactly where that crosses over is clearly arguable...there is a gray area.
- Less than 40m, NDL, apparently no argument that this is recreational. So 40m to maybe 50m, NDL, is in the gray area between a recreational dive and a technical dive.
- What about deco? No deco (and not too much depth) is clearly recreational; lots of deco is clearly technical. For the sake of argument, let's say that 5 mins of deco at 3m, using backgas, is "light deco." Let's say that required deco at more than one depth, is "deco." Then we define the technical dive as requiring deco for more than 5 mins at one depth or at more than two depths.
- Helium: air is acceptable for all agencies up to 30m, but additional He is sometimes included for greater depths. Certainly deeper than 60m, He is mandatory for all agencies. The gray zone is 30-60m for He. If you are using He, it is a technical dive, by definition herein.
- Oxygen: Nitrox is extremely popular in recreational diving, for the increased bottom time; up to 40% is the usual training. Greater than 40% is the realm of advanced nitrox for deco, 50, 80, and 100% being popular. Hypoxic mixes (less than 21% O2) are reserved for deep dives, typically greater than 60m. So the clear recreational regime for oxygen is 21-40%: for technical the oxygen content is darn near anything, with low percentages for really deep and high percentages for deco.
- Nitrogen: N2 is 79% is air, and only varies from that in recreational diving if Nitrox is used, i.e. replacing some N2 with O2. If the N2 varies from 79% due to the addition of He, then it is a technical dive.
The Diver (i.e., the person....not the dive)
Based on observation and anecdote, the vast majority of divers have minimal training beyond OW, do not dive with redundancy (except for an alternate 2nd stage), do not plan their dives based on mission, gas usage, staying within NDL, or expectation of any equipment faults or other unanticipated issues, do not really stick with their buddies, ascend too quickly from their safety stops, and do not log their dives. This is the realm of the purely recreational diver, who may care little about trim or propulsion techniques, and is there to see the reef, swim around the wreck, or look for sharks.
The agencies view the recreational divers as those without any technical training, and tend to be vague about how much and which technical training turns the diver from a recreational diver into a technical diver.
At the very least, in the TDI sequence as an example, the Advanced Nitrox/Deco Procedures course is the clear entry point to technical diving. There is an introductory course, Intro to Tech Diving, but it is an introduction to the skills needed in tech diving without going into any details or giving much practice. The first real tech course is Advanced Nitrox, which teaches the use of O2 from 21% up to 100% and thus address the fourth bullet above; no deco is involved, and no depths greater than 40m. The second real tech course is Decompression Procedures, which teaches use of a decompression cylinder, trains to 45m. The third is Extended Range, which trains to 55m. The PADI sequence is similar, with Tec 40, 45, and 50. These examples move through the transition from recreational dives -- no extra gas or equipment needs, no deco, no Helium -- through light deco, into real deco on real dives with quite hard virtual ceilings. The key distinguishing feature in all the training is not that depth is the single discriminator for what makes a dive technical, but rather deco is the primary discriminator. Depth is simply what makes deco so very likely; depth is what makes Helium so very likely; and depth is what makes hypoxic mixes so very likely.
Thus, the recreational diver becomes a technical diver when they learn how to manage deco (whether cause by depth or just by long dives at moderate depths), and how to manage the other things that depth might require, namely gas changes, extra cylinders, redundant equipment, and dive planning.
Because all these new things the recreational diver must learn and get skilled at can be taught or self-learned in various sequences and with varying emphases, there is not a hard boundary one crosses to become a technical diver...there are "baby step" involving deco, gas mixtures, equipment, planning, etc., that are appropriate to "baby dives," yet each of these steps can become more involved and move critical to survival as depth and/or deco increases.
It might be argued that the agencies have tacitly decided that a "full-fledged technical diver" is one that is trained through trimix with hypoxic oxygen and multiple deco cylinders plus back gases and travel gases. so that "all" depths can be accessed. Of course, in these extremes, CCRs come into play as being more and more the tool fo choice, if only for the cost of helium and the number of bottles one can conveniently carry. NOTE: CCRs are just a very technical way to manage the bulleted aspects (listed above) that need to be managed on a dive.
Summary
The recreational
dive is one that has no special demands regarding depth, deco or gasses. Above 40m, NDL, Nitrox at less than 40%. Good agreement.
(The coarse definition of a technical dive is one that is beyond recreational in terms of depth, deco, and gasses.)
The gray area is deeper than 40m-50m; deco of less than 5min at 3m is "light gray;" depths to 50m are gray; normoxic He is "dark gray."
The technical
dive is one with special demands on depth, deco, or gases, thus special demands on equipment to address those those demands. It unequivocally involves depths below 50m; deco of more than 5mins at one depth or deco at two depths or more; oxygen over 40%; helium and hypoxic oxygen.
If one does a technical dive -- as just defined -- then one should mitigate the increased risks of that dive by having the appropriate training, experience, and equipment, and should plan the dive accordingly.
A recreational
diver is one doing a recreational dive, whether that diver has done technical dives or not.
A technical
diver is one who is doing a technical dive and is trained, equipped, and following established procedures for that dive, including pre-planning. A technical
diver who is doing a recreational dive may plan the dive, but as there are no special needs in that dive for gasses, equipment, or deco, then it is not a technical dive...it is still a recreational dive.
