Am I being a scuba prude for having this leave a bad after-taste in my mouth? I mean, I was not planning to venture into the technical realm just yet. As a recreational diver I am inclined to stick to the limits suggested by PADI. 5 meters deeper than 40 just because its more thrilling (or whatever their reasoning) seems like asking for trouble to me. Am I alone in these thoughts? Feel like I'm on a rant here, but I'm very curious if this is an exception or if this actually happens a lot in dive centers (i.e. customers asking to dip their toes a little beyond the recreational realm (especially when it comes to depth and deco stops) and dive centers agreeing.
I am not a technical diver and so I have not taken the great Oath of Silence, the mantle of responsibility of never divulging the secrets of technical diving to those who have not gone through the formal training that is the one and only way that makes it safe to harbor this knowledge.
I think it would be useful, when this topic comes up, as it does perennially, to actually talk about the things a responsible technical diver might do for a dive like this. I'll try, even though I haven't had the formal training.
For those of us more accustomed to feet, a 45 meter dive is 147 feet. I'm presuming this dive is done on a single gas.
1) Conducting a responsible dive to 147 feet would require actual gas planning individually and as a team. All divers would have to have an accurate, realistic assessment of their SAC for the conditions of the dive. While gas planning is, nominally, taught in OW and revisited in AOW and Deep Diver classes, it is unusual for recreational divers to plan their gas usage in a thorough, formal way, that includes contingencies and covers the varying needs of each member of the dive team.
2) A diver conducting a responsible dive to 147 feet would have a redundant air supply available so that the dive could be completed safely in the event of a loss of gas, even if a buddy is not available to share gas. Either backmount, manifolded doubles or sidemount doubles would be considered suitable for this. In either case, training in normal and emergency procedures for the chosen system would be customary and would be drilled to the point where the actions are rapid and automatic. It is my understanding that a pony or stage bottle alone, even if sufficient from a gas planning standpoint, is not considered sufficient at this depth.
3) Each diver would carry redundant instruments for measurement of time and depth, in most cases in the form of a backup dive computer. Each diver would be intimately familiar with the operation, during a deco dive, of their primary computer and (if different) their backup computer.
4) The dive would ordinarily be planned with an effective external means of controlling depth at the decompression stops, such as the use of an anchor line, shot line, upline, or SMB, rather than relying solely on control of buoyancy. The divers involved would be familiar with the use of each of these, during deco, and would have practiced with them. This would be done despite the fact that divers contemplating such a dive would be expected to have excellent buoyancy control skills.
5) The possible effects of narcosis would be considered, and depending on the nature of the dive, diver preferences, gas availability, cost considerations, and the agency whose training is being followed, a gas mix including some helium might be used. If so, this would lead to its own set of procedures and protocols for blending, analyzing, and marking cylinder contents.
6) Typically this would be a dry suit dive. If conducted using wetsuits, particular attention would be given to contingency planning for BCD failure.
7) By the book, there would be some formal contingency planning for foreseeable problems, a risk assessment, and some drills prior to or during descent. I don't know whether these are honored any more in practice than BWRAF or not. Minimally, this might result in making sure oxygen is available at the surface, for example, or making sure there is a safety diver on deck who has additional deco gas available.
The point here being that it's not just about holding a different color C-card. Conducting dives to these depths, safely, requires different equipment and procedures, and requires the automatic reactions that come from actually doing the drills.
