Sharing air to extend bottom time

[DevonDiver]

While you are imagining things, see if you can imagine short fills or limited tank size availability.

I can imagine those - but, luckily, I can also imagine checking my fill at a point where it can be rectified... and also imagine sidemounting, so that tank size becomes irrelevant for recreational dives.

Anything else irrelevant and solvable I need to ponder over?

 

[tflaris]

We are in mostly sunny and somewhat rainy Riviera Maya for a week.
Of course we booked some diving during this time.
Being new divers we opted to hire a personal DM.
First day comes along and I had trouble equalizing my ears so not wanting to waste too much time i decided to head back on the boat and at least let my husband go ahead and enjoy the dive.
Thinking back now i think was more of a psychological issue, since the rough seas made me quite uncomfortable even on the way to the dive site but more so once i jumped in the water.
Next day was all nice and calm and we had a good dive at 11.30.
On the way back we decided to stick around and do one more at 2.30, on which just before the dive he asked us if we are OK if there is one more person other than us two.
The DM was great, the briefing i felt was adequate.
The plan was to let him know when we are on 700psi and we would be heading up to our safety stop.
On the 11.30 dive all worked according to plan, once we motioned that we are on 700psi he deployed the sausage, which tbh i thought it definitely needed some viagra, and we made our way up.
Second dive was a different story.
700psi come along and we motioned to him, at this point i am expecting to see him reach for the sausage but its not happening. Being a new divers you can perhaps imagine our confusion.
Next thing i know he gets close to me, looks at my gauge and proceeds to hand me his spare and we go along for a while sharing air.
I have to admit that this confused the hell out of me. At first i thought wth is he doing, is he gonna let me run our of air and i'll be resting here with the tortugas?
Eventually he handed me back my own regulator, at this point 500psi were left.
During the time i was breathing from his spare i tried to make sense of what was going on and all i could think of was that he wanted me to save the air i had left for the safety stop and to safely get back up...but that didn't quite make sense since my husband was on 700psi at the same time as me, so at this point scary thoughts were going through my head, meanwhile we are being "attacked" by some big fish that was very attracted to the yellow of the spare and insisted on nibbling on it, he hung around us all the way to the surface. At one point when i turned around I had this fish with a big open mouth right in my face lol.
So back on the boat the DM said that actually the reason we shared air was because he still had 2000psi and to prolong the dive a bit longer.

So here comes the question...is this OK, is it common practice?

As a NAUI Instructor I would not recommend this behavior. a good safety rule is to use 1/3 of your air supply down and swimming out. When you reach the selected turn pressure (say 2000) signal to your team to turn the dive and swim back to the point of origin. This gives you plenty of gas for navigation errors and or emergencies.

On a drift style dive the only difference would be to use 2000 PSI (or 2/3's the gas supply) in one direction. When reaching the selected turn pressure (1000 PSI) signal to the team to make a slow safe controlled ascent to the surface and perform a 3 minute floating safety stop and surface to get picked up by the boat.

Hopefully you are using a SMB or Dive Flag on Drift Dives.

Hope this helps

Tony Flaris
NAUI 44662

 

[windapp]

Did you enjoy the extended bottom time or were you too nervous to enjoy it since you didn't have a clue what your divemaster was trying to accomplish? I personally don't like surpises on a dive.

 

[Tigerman]

I can imagine those - but, luckily, I can also imagine checking my fill at a point where it can be rectified... and also imagine sidemounting, so that tank size becomes irrelevant for recreational dives.

Anything else irrelevant and solvable I need to ponder over?

Actually, when you start talking sidemounting, that IS irrelevant to basic scuba and rec diving (wich is the part of the forum were in)..
That aside, if youre not managing your tanks yourself, like when you go with a op that take care of all the manual labour for you, the first time youll even see the tank is when youre already on the boat and ready to kit up. If its a short fill you may be able to find another, better filled, available tank, or not. These ops might also not have other tank sizes available so youll have to go with whats there..

 

[DevonDiver]

Actually, when you start talking sidemounting, that IS irrelevant to basic scuba and rec diving (wich is the part of the forum were in)..

Ignorance doesn't win arguments. Sorry - but you're just plain wrong.

Gas redundancy IS relevant to basic scuba and rec diving.
Gas sufficiency IS relevant to basic scuba and rec diving

Aren't those the two issues at the core of this recreational diving thread?

Here is some relevance:

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PADI Recreational Sidemount

The philosophy of this course is to provide an introduction of the benefits and proper configuration of the use of sidemount equipment for recreational diving, with
an emphasis on safety. The goal of this course is to provide a systematic, methodical, approach to recreational sidemount diving, showing how to apply the skills developed using conventional backmounted equipment. Once certified, student divers will be able to use sidemount equipment comfortably for no stop recreational dives in conditions similar to, or better than, those encountered during training.

Course goals are to:
• Explain the benefits of sidemount diving
• Develop student ability to assemble, configure and wear sidemount diving equipment
• Guide students in the skills


Prerequisites: PADI Open Water Diver
Minimum Age: 15 years
Minimum Water Sessions: 1 confined water dive / 3 open water dives

A. General benefits of sidemount

As you probably realize, in sidemount, divers wear one, or more commonly two, cylinders along their sides with no cylinders on their backs.


B. This configuration originated with cave diving, but has a growing following in recreational diving because it has these general benefits:


1. Ease of streamlining equipment. When you need or want more than one cylinder, sidemount provides a very streamlined package. When correctly configured, sidemount can reduce drag and avoids contact with the environment.
2. Easier equipment transport. Most people find it easier to carry and wear two smaller cylinders instead of one large cylinder. Divers with physical challenges may find this a big advantage, especially in that it allows them to don equipment in the water.
3. Versatility. Sidemount works well with many recreational diving activities making it a great way to expand your capabilities with a single basic configuration. Divers with physical challenges find that even when diving only one cylinder, sidemount simplifies getting in and out of the water.
4. Increased gas supply. Using enriched air nitrox and an EANx dive computer, you often have so much no stop dive time that you run out of gas long before you approach a no decompression limit. The ability to use two cylinders lets you enjoy more of this no stop dive time.
5. Accessibility.In sidemount, the regulator first stage and valves are in front of you where they’re visible and accessible. This makes it easier to spot and deal with problems (you’ll learn about this during the course).
6. Adjustability. Most sidemount configurations allow you to fine tune equipment fit and trim during the dive to enhance streamlining and body position. Most divers find this makes sidemount more comfortable than other configurations.
7. Problem solving. With two-cylinder sidemount, you can handle an out-of-gas problem without your buddy as your primary alternate air source.

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As an aside, I've been doing ALL of my recreational diving (and technical, for that matter) in sidemount for the last 6 months. A lot of dives. It's wonderful. Go out for a two-tank trip - wearing both tanks for both dives - loads of gas, total redundancy, very comfortable and stable in the water. No more hassle than diving single-tank back-mount... in fact, easier, because I don't have to lug a BP&W with cylinder attached on and off the boat....and no tank changes needed between dives.

Oh yes... and tanks are prepared/rigged at the dive center - so I check the pressure (and nitrox %) there and then.... long before I get on the boat.

That aside, if youre not managing your tanks yourself, like when you go with a op that take care of all the manual labour for you, the first time youll even see the tank is when youre already on the boat and ready to kit up. If its a short fill you may be able to find another, better filled, available tank, or not. These ops might also not have other tank sizes available so youll have to go with whats there..

Your dive.... your kit.... your responsibility. Take it or leave it.

Did you ever think to ask a dive op if you can check and label YOUR tanks prior to loading? No? Oh.......

 

[Tigerman]

Good for you that you can check the tank at the dive center DD, good for you if you can use YOUR gear all the time, but that just IS NOT THE CASE for everyone, especially not divers who have to travel to be able to dive.
Also in a lot of locations the tanks is handled by a "central filling station" not located at the dive shops, which means not even the shop get to test the tanks untill they are delivered.

You(and the agencies) can call the sidemount course recreational or tech or whatever, but how many rec divers do you really see with sidemounts? It IS for all intents and purposes irrelevant as its just not what most divers do.

 

[DevonDiver]

Good for you that you can check the tank at the dive center DD, good for you if you can use YOUR gear all the time, but that just IS NOT THE CASE for everyone, especially not divers who have to travel to be able to dive.

Also in a lot of locations the tanks is handled by a "central filling station" not located at the dive shops, which means not even the shop get to test the tanks untill they are delivered.

As a customer, you don't have to accept something that you're not happy about. Attach your regulator, crank a valve.. hey, presto! If it's a low fill, then refuse it... then it's the shop's problem.

I don't see what the issue is here. If you're worried about short fills, then check your tanks before it's too late.

You won't convince me that it is impossible to check a tank before you depart on a boat etc. Just turn up a little early, if necessary... what's the problem?

All part and parcel of being a diligent, well-prepared diver IMHO.

Of course.... that's all ignoring the point I've been trying to get across - about the use of two tanks for a dive. That solves the issue of low-fills. It solves the problem of insufficient gas for the planned dive, especially where nitrox is used. It solves the problem of redundant gas for emergencies.

Go figure... you argue that insufficient gas is a problem... and then you argue that having extra gas is irrelevant. Not got the logic sorted on this one yet?

You(and the agencies) can call the sidemount course recreational or tech or whatever, but how many rec divers do you really see with sidemounts? It IS for all intents and purposes irrelevant as its just not what most divers do.

Ah, ok... so it's just me... a sidemount instructor.... and the majority of agencies - that supply sidemount courses to a rapidly expanding demographic of recreational divers... that don't know what we're talking about? LMAO

The fact is that 90% of 'rec' divers don't even know what 'gas redundancy' or 'gas planning' is - that's an issue. In fact, it is THE issue that started this thread.

As an established contributor to Scubaboard, you are not ignorant of such issues... so why hide behind those issues now, when faced with a solution that defies your debating stance on the 'need' to muddle through dives on a single tank that doesn't hold as much gas as you actually plan for/need?

What 'most divers do' and what 'most diver should do' are two entirely different notions. If there was no discrepency between those two states, then we'd have very few fruitful discussions here on Scubaboard. Are you really going to drag this debate to the lowest common denominator - and suggest that divers should just 'follow the herd' and do what the majority do... even if they know better???

We can help resolve that issue by educating divers about effective and safe solutions to their ignorance.......or we can stick our heads in the sand, use bastardized solutions for eeking out a few extra minutes on a dive and blinker ourselves to what our real options are.

I see you've gone for the latter course of action?

 

[Teamcasa]

...We can help resolve that issue by educating divers about effective and safe solutions...

We already have.

 

[DevonDiver]

We already have.

You mean the one that:

1. Is only recommended to 'experienced' divers of some undefinable skill and comfort level?

2. Is not taught, or recommended, or sanctioned by any agency on the planet?

3. Ignores all manner of gas planning and self-sufficiency advice that we'd otherwise give?

4. Willfully disregards all other solutions, because they might not be 'as convenient'?

5. Risks bystander/diver reaction, if misinterpreted as an emergency?

6. Would leave any dive pro in serious liability jeopardy?

7. Encourages divers to deviate from standardized and prudent safe diving practices?

 

[caseybird]

On a drift style dive the only difference would be to use 2000 PSI (or 2/3's the gas supply) in one direction. When reaching the selected turn pressure (1000 PSI) signal to the team to make a slow safe controlled ascent to the surface and perform a 3 minute floating safety stop and surface to get picked up by the boat.

Hopefully you are using a SMB or Dive Flag on Drift Dives.

Hope this helps

Tony Flaris
NAUI 44662

This is great, your instructions exactly mirror the course outline I posted above, (see post # 143). The only difference is that all divers reach 1000 psi using my system.
Thanks!