Planned deco on a recreational dive?

[Patoux01]

This conversation is terrible, and the mods should shut it down.

No it's not, and no they shouldn't. I thought NZ was the land of freedom?

 

[BEVANJ]

Well put boulderjohn.

 

[Patoux01]

Let's just remember that in France you'll be allowed to do deco under supervision and it'll hardly require any kind of redundancy (as a matter of fact, there's no required equipment) and the guide is only required to have 2 separate 1st stages.

Furthermore, let's add that BSAC and virtually all of CMAS do deco diving straight from their 2nd level of diving, without any of them at any point calling their diving "technical diving".

Would be cool if we could let it that way, because stuff like is kind of annoying:

Computer failure? Do you have a backup? Yes, my buddy has one.
-Different decompression algorithms. (VPM-B, Buhlmann etc) They'll all get you out
-Loss of a deco gas? There's none here
-Loss of backgas? (in this case single back gas - a very real possibility).
-Narcosis (in this case, deep air dive?!)
-PPO2 - what is acceptable on the bottom? What is acceptable for deco? Air po2 is fine to 50 something meters.
-OTU exposure. irrelevant in this kind of scenarios
-Redundant breathing gasses.
-Selecting optimal deco gasses for the planned dive. irrelevant in this kind of scenarios
-Logically sorting deco gasses on your rig. irrelevant in this kind of scenarios
-MOD calculation. irrelevant in this kind of scenarios
-Gas planning (SAC rates, etc).
-Medical training for dealing with DCS etc. If they don't carry a chamber, it's not gonna be much useful. Give O2 and call for the correct helpline, not much different from OW to advanced diving
-Spare kit which should be carried (scissors/knives/spare masks, etc). Lolwat.
-Discussing as a team various failure scenarios.
-Practicing feathering valves on free-flowing regulators. Lolwat.
-Smb usage.
-Fixed vs dumpable weight. (Which is really better for deco diving?)
-ETC, the list goes on...

I just put in bold the things that do not matter and added some comment...

 

[MXGratefulDiver]

Wow. As a relatively new member to this forum, and as a TDI Adv nitrox + deco, CCR diver, reading this makes me want to flee.

DIVE WITHIN YOUR QUALIFICATIONS. YES, THAT'S A FULL STOP. No if's, no but's.

There is so much that people don't think about that can go wrong.
-Computer failure? Do you have a backup?
-Different decompression algorithms. (VPM-B, Buhlmann etc)
-Loss of a deco gas?
-Loss of backgas? (in this case single back gas - a very real possibility).
-Narcosis (in this case, deep air dive?!)
-PPO2 - what is acceptable on the bottom? What is acceptable for deco?
-OTU exposure.
-Redundant breathing gasses.
-Selecting optimal deco gasses for the planned dive.
-Logically sorting deco gasses on your rig.
-MOD calculation.
-Gas planning (SAC rates, etc).
-Medical training for dealing with DCS etc.
-Spare kit which should be carried (scissors/knives/spare masks, etc).
-Discussing as a team various failure scenarios.
-Practicing feathering valves on free-flowing regulators.
-Smb usage.
-Fixed vs dumpable weight. (Which is really better for deco diving?)
-ETC, the list goes on...

There is so much thought which NEEDS to go into deco dive planning in order to do it safely. If you want to do it, get qualified, and find a good instructor at that.

Advocating for someone doing 10min of deco on a 45m dive, on a single tank is ridiculous. If anyone has a reg failure, and they wind up buddy breathing, the person gas sharing is probably going to run low, if not out of gas. Also, try holding stops, whilst sharing air on a standard recreational setup with a short hose, without any practice. I'm sure it wouldn't be fun - even after you have practiced it. That is one of the MANY MANY scenarios that could go wrong without the proper planning.

On a dive with 10min of deco, if someone doesn't realise that their computer is actually on the lenient side of the scale, as opposed to conservative things could easily go wrong. Something as simple as having a mask kicked off by an errant fin resulting in having to surface after no one else noticed (were they carrying a spare? Suspect not.) could result in a trip to the chamber.

Hell, I personally know people who have taken a bend within the realms of their NDL or staying within their computers decompression. And yes, the computers decompression model was relatively conservative.

This conversation is terrible, and the mods should shut it down. People are advocating for others diving outside of the limits of their training.

Flame me for being the new guy and saying this, I don't give a toss.

Bevan

I can agree with the gist of your message ... folks should go into any dive with a sufficient dive plan, and adequately prepared to deal with any failure they're likely to encounter. Gas loss is certainly at the top of the list, since not being able to breathe tops the potential emergencies one may have to deal with. But it's not the only failure one should be prepared to deal with, and your list is a pretty comprehensive one.

That said, I disagree that the conversation should be shut down. Don't know how it works in New Zealand, but in the USA the "just say no" approach has proven ineffective in pretty much every circumstance it's ever been tried. Far better to give people information ... even in some cases bad information ... and let them make their own choices. Presumably we're all adults here, and capable of making our own decisions.

Dealing with deco isn't rocket surgery ... but there are some fundamental principles that should be applied if one is to conduct their dive within the parameters of acceptable risk. The best way to learn those principles is through a class, because that way you don't have to apply your own filter to remove the scatological particles from the information flow. However, one can pick up a lot of useful information by reading other people's opinions, as long as they recognize them as such.

... Bob (Grateful Diver)

 

[Gareth J]

I'd just like to add a little more about the BSAC structure.

Like PADI OW, the BSAC Ocean Diver is the basic entry level. They both teach more or less the same thing, which is the basic minimum you need to make a successful dive.
The only basic difference I can identify is a state of mind. Even at OD (Ocean Diver), divers are taught their survival is reliant on their buddy, and their buddies survival is reliant on them. Not on any other third party. There is an expectation that they are diving together, alone, as a self reliant buddy pair. i.e. without a guide.

I often say to students, at OD level that we teach them the basics of diving, (buoyancy, mask clearing etc), and how to get their buddy to the surface in the case of an incident. Once they get their buddy to the surface, their is an expectation that they are diving with a branch, and surface cover will take over the rescue.

BSAC Sports diver is closer to PADI rescue diver. In the BSAC SD (Sports Diver) course the rescue skills are extended to greater depth, more stressful scenarios and better skill levels. In addition, surface rescue skills are introduced, tows, Rescue Breathing, Chest Compressions and diver recovery to the boat/shore.
The rescue side is one half of the course. The second is the extended diving skills and knowledge. Which includes dive planning of decompression dives. Both Nitrogen management and gas management. Redundancy is covered. Additional diving skills and technique.
So there is a lot more taught at this point than by PADI certainly, and most other agencies. The one exception is probably GUE.

The other point, which may well be the more significant. Is that although there is a commercial arm to the BSAC, and these course are taught by dive schools. Most core diver training (OD, SD and DL) is taught in branch. As such, a lot of diving is occurring between and during courses. There is normally a mix of abilities, and a range of diving. A lot of what is taught in BSAC branches is unofficial through friends and buddies. From how to load boats, to why some are diving twinsets.

There is also formal and informal oversight. Formally OD's won't be on trips where the diving is beyond their 20m limit, or at least, they won't be diving the wall below their 20m limit, although some on the boat might be at 50m.
Informally, the group will manage what dives they do and the site. Putting two Ocean Divers on a dive together on a benign site that they have probably dived before - where they are running the dive themselves, modifying their dive plan if required. Or putting them on a dive with a more experienced buddy, where they are gaining experience.

Branch (club) diving, there is a blurring of formal, and informal tuition. Whilst this does occur outside the club structure, is much more noticeable inside the club structure. The best way for a new diver to improve, is to go diving, add to that a group of experienced buddies, then the new diver is more likely to progress quickly and continue to keep diving. (And hopefully to avoid some of the stupid (risky) mistakes some of us have made!)



Gareth

 

[gfaith]

"Apply your own filter to remove the scatological particles from the information flow."
... Bob (Grateful Diver)

I want to steal that one.. Well said.

 

[MXGratefulDiver]

I want to steal that one.. Well said.

Thanks ... and steal it with my blessing ...

... Bob (Grateful Diver)

 

[scubadada]

Hi @Gareth J

It's been a while since I looked at BSAC training. I may be wrong but don't Sports Divers do a simulated decompression dive but not an actual decompression dive? In addition, don't they have a depth limit that is increased with appropriate experience and supervision post certification as a SD? When do divers perform decompression dives?

Thanks, Craig

 

[KenGordon]

Hi @Gareth J

It's been a while since I looked at BSAC training. I may be wrong but don't Sports Divers do a simulated decompression dive but not an actual decompression dive? In addition, don't they have a depth limit that is increased with appropriate experience and supervision post certification as a SD? When do divers perform decompression dives?

Thanks, Craig

They can do actual deco dives once they are qualified. The initial qualification is 20m, extended by 5m at a time over a few dives. Typically there will be a few of those before they end up able to dive to 35m depending on the sites and people diving. If a club has a number of trainees then the organised dives have to take that into account, so it is unlikely they will be doing 35m directly after qualifying. The deco will follow if it turns out to be required. Often it will be second dives that lead to the deco.

The point isn't that people go looking for deco dives to do. They do dives and some happen to lead to deco. Given proper planning and buddy procedures this is not a problem.

This is not the same as someone with 4800l of back gas and an ali80 of 50% looking to max out their bottom time at 45m. If they want to do that there are further courses to do.

 

[Lorenzoid]

Is there a cultural element to this? It sounds like BSAC (and CMAS?) treat divers as though they are capable of setting and following limits. On this side of the pond, I suspect the agencies set hard limits defining "recreational" diving out of concern that teaching divers to do "a little deco" opens the door to limit creep, and divers can't be trusted to seek (and maybe won't know at what point to seek) the training to do more advanced deco dives.