part of the issues with doing those long dives at the end of class for the instructor is mandatory deco, especially lots of it come with a lot of risk. Much better to hit the depth limit and not incur mandatory deco for the skills to be done at the surface in case anything goes sideways. At a roughly 1:1 ratio of bottom time to deco time at 50m, it's better to not spend that much time at depth and rack the time up on ascent where if something goes wrong, you can make a more direct ascent to the surface
You have ample opportunity on dives #1 and #2 to develop, refine and rehearse skills.
As an example, this is how I approach teaching Tec50...
Dive #1 is shallow/confined water. It's possible to spend an extensive amount of time repeatedly
drilling protocols and further raising the standard of
fundamental skills. I typically spend an entire day doing this and it can be exhausting. 2-6 hours of practice time is the norm, but we take breaks to hydrate and warm up as and when needed. In nearly every case, there's a lot of valuable development that can be achieved. Quite often, my students elect to extend this phase of training over multiple days... to enable very high levels of competency to be achieved. In that case, I also add numerous skills (
beyond the bare minimum syllabus) that add to their 'toolbox' and give them more options and experience for future contingencies.
Dive #2 follows on. I run this as a
dress rehearsal dive. I make it as realistic as possible, whilst only the actual decompression is simulated. I have to see that the student is fully competent to plan, organize and conduct the dive, as well as dealing with reasonably foreseeable contingencies, without any input needed from me. They have to handle all the logistics and preparation. This dive has to be 'passed' before I can be reasonably confident that the diver is ready and able for actual extended range decompression diving. Typically, I will choose a low-visibility site, and the ascent will be done with either a DSMB or by visual reference on the line only (
i.e. all deco in neutral buoyancy, horizontal trim maintaining team formation and positioning).
Dives #3 and #4 are check out dives. They are
assessed... pass/fail...and the student has to conduct both dives, with
no instructor intervention (
beyond fulfilling a normal team role in-water). If I have to intervene to preserve safety in any way, the dive is a 'fail'...and not counted towards certification. Runtime is calculated by the student based on gas consumption and available back and deco gas. Twin AL80s at 3000psi/200bar are used for backgas. The student can select from AL40 or AL80 deco cylinders, again filled to 3000psi/200bar. I expect them to
maximize bottom time based on the resources they have available, but with the caveat of using prudent ZHL-16C GF settings for dive planning.
I teach technical diving, not glorified bounce diving. Technical divers plan and conduct dives (
at great expense) with a purpose in mind.
Bottom time is important, it's why we DO these dives...and
divers must be familiar with the psychological and physical pressures of having the substantial deco obligations that arise from spending meaningful time at depth.
I don't emphasis the performance of 'skills' on dives #3 and #4. Frankly,
the student diver shouldn't yet be doing the dives if further practice of the skills were necessary. For me, dives #3 and #4 are about the APPLICATION and ASSESSMENT of the competencies learned previously. I don't do any contingency/emergency skills during the bottom phase... and brief this point.... because I want no confusion or hesitate should a real emergency arise at depth. It's a real dive, with real consequences... so the role-playing should be reserved for the simulated dives. The few skills mandated for the dive are conducted shallow, once all decompression has been completed.
Whilst Tec50 (Extended Range) does require basic tech skills to be raised to a higher level of consistency and accuracy... this course is, IMHO, about
DOING THE DIVES. It's about drilling hard in the shallows, but then after, using the training dives to amass operational experience and the application of competencies. Sacrificing that APPLICATION in favor of a few more fruitless repetitions of skills (
that should already be fluid from the shallow training) is entirely self-defeating and robs the diver of the EXPERIENCE they need to be truly competent.
Lastly, Tec50 is the prerequisite (
and to an extent, preparatory) training for trimix. Doing pathetic bounce dives at this level only serves to leave the student woefully unprepared for any subsequent development they wish to pursue.
Students do this training to enable safe diving at the appropriate level.... NOT to be told they should reverse to their previous level and take weeks, months or years to progress to the level IN WHICH YOU JUST QUALIFIED THEM TO DIVE.
If there are performance flaws which provoke the instructor to doubt the student's competency to perform safely and reliably AT THE CERTIFICATION LEVEL, then they should remedy those flaws
before certification is issued.
The attendance / set-duration course mentality should stay put in the world of recreational diving (
actually, it should be eradicated from there also....). This abject unwillingness to run truly performance-based, training-focused, courses is the ONLY reason why a tech instructor would minimize bottom times and/or counsel students NOT to dive at the level to which they are being certified.
