An interesting dive

[matjo1]

I did it once, when a guest was using his air too quickly and we wanted to go to a particular site. I put him on my octopus when he still had a half full tank. Once we got to our destination his consumption reduced. It was a drift-type dive anyway, so after we'd done what we wanted to do we surfaced, with him back on his own tank.

It's only the once, but in similar circumstances I'd do it again. I don't see any safety implications at all. Mind you, the diver needs more training to reduce his air consumption.

I just don't know. I guess this is a gray area of diving, that depends on so many different factors. To do it with a diver that you just met versus one you dive with every day is very different.

 

[diver 85]

I just returned from a week of diving in Mexico. During one dive (the group was the DM, another diver, my wife and myself), I looked over & noticed the DM sharing air with the other diver AS THEY CONTINUED THE DIVE. I signalled to ask if he was ok, and he returned the "OK" signal. I then "thumbed" the dive myself.
On surfacing, the other diver explained that he uses a lot of air & was running low. The DM explained that he was sharing air so that we wouldn't have to cut our dive short. Needless to say, I was stunned, and I was wondering if this was an isolated incident or if this is common DM practice.

Rare happening for me, but why did you thumb the dive???..If nothing else, why not ask before thumbing it to see his air supply left??...You probably wasted some bottom time, IMO........Always remember, you (& your buddy---I'm assuming here) are certified divers........I guess you can say no dumb DM is going to cost me UW time....

 

[littlejohn]

Question:

Why is it most all the dive boats use AL 80 tanks?
Being a newer diver and a bit of an air hog I have gone to larger tanks of my own.
Al 100's don't cost much more then the 80's yes they are big but most guys over 6' can handle them with no problems

 

[TheWetRookie]

I have partaken in this activity also at the beginning of my diving. It was pre-planned with the experienced diver that I was diving with. At a set air pressure on my guage she gave me her long hose and we carried on the dive. Side by side. When she reached her set pressure I switched back to mine and then we headed back to shore. All went smoothe with and we had a good dive.

 

[Teamcasa]

Question:

Why is it most all the dive boats use AL 80 tanks?
Being a newer diver and a bit of an air hog I have gone to larger tanks of my own.
Al 100's don't cost much more then the 80's yes they are big but most guys over 6' can handle them with no problems

Its a cost issue. AL 80's are durable and inexpensive.

 

[phyrekat]

Rare happening for me, but why did you thumb the dive???..If nothing else, why not ask before thumbing it to see his air supply left??...You probably wasted some bottom time, IMO........Always remember, you (& your buddy---I'm assuming here) are certified divers........I guess you can say no dumb DM is going to cost me UW time....

I was just so surprised to see it & when I figured out what they were doing (when he signalled me back that they were OK), I realized that they were continuing the dive for my (and my buddy's) benefit. I didn't see any reason to take any unnecessary risks for an additional 5-10 minutes of bottom time.

FWIW, the other diver did finish the dive with an (almost) empty tank. What happens if, for some bizarre reason, the DM's air fails? I guess that's the issue I had with the whole thing. Why invite trouble?

 

[TSandM]

When I reach safety reserve (rock bottom) the dive is over, period. If, for some reason, I have an equipment malfunction or gas loss and have to go on someone's long hose, I am by definition below safety reserve, and the dive is over, period.

HOWEVER . . . Peter's SAC rate is about .6; mine is .4. If we are diving in the tropics on the same sized tank, Peter's gas consumption will cut our dive short while I still have a lot of excess in my tank. For that reason, and only EARLY IN THE DIVE, Peter will go on my long hose for a while. I not only don't think that's dangerous, I think it's a good thing. We get the practice of air-sharing and swimming while sharing gas; both of us have oodles of our own gas, so even if somehow we got separated, there's no problem. And we end up with equalized gas consumption.

We have had problems with DMs seeing us do this (even, sometimes, after we have explained that we are going to) and literally freaking out, and I've had a PADI instructor tell me that he felt it was unconscionable, because once you are sharing gas, the only thing you can do is an immediate ascent. But we're CAVE DIVERS . . . If we share gas, we swim out. I think it's good to practice that.

 

[redacted]

My wife/buddy and I have about the same SAC but, if one of us gets a short fill, we will balance our gas by sharing air. We usually wait until later in the dive when we are already into an ascent and the short tank is down to 1000 psi. Then we share air until the 2nd tank is also down to 1000 psi. Then we switch back and proceed with ending the dive. I don't see the problem some of you seem to see. If you are not comfortable sharing air, then maybe you should consider some other activity.

 

[Ice Mike]

Relax take a deep breath and tell someone at home how you feel.

Sorry if I misread your post on UW return to the boat being OK.

To do so to CONTINUE a dive is NOT OK, IMHO = IN MY HUMBLE OPINION.

Let me be clear: "I do not agree with your opinion (humble or not)."

I agree with the post made by TSandM. Can't say it any better myself.
Not only do they continue the dive, the airsharing is even part of their plan. (In addition to good practice for other dives they want to do. )

Where on this thread do you see where ANYONE is using DOUBLES?

Nobody said it and I wanted to bring it up.

When I see somebody diving independant doubles (eg, sidemount) and I see that person switching between tanks continously during the dive, I don't think it is unsafe.
I think that it is smart to balance the amount of gas in the tanks and to keep checking both tanks are in working order.

When TSAndM and husband are diving, they balance the amount of gas in both tanks. I don't see the need for stopping the dive even though one has more than enough gas left.
If this practice is carried out to the extreme, they would start their final ascent with equal amounts of gas in either tank. Where the amount in either tank is still enough for both divers in an emergency.

I my opinion all they have done is maximise the amount of dive time even though they started with equal amounts of gas and unequal breathing rates.

 

[MikeFerrara]

When I reach safety reserve (rock bottom) the dive is over, period. If, for some reason, I have an equipment malfunction or gas loss and have to go on someone's long hose, I am by definition below safety reserve, and the dive is over, period.

HOWEVER . . . Peter's SAC rate is about .6; mine is .4. If we are diving in the tropics on the same sized tank, Peter's gas consumption will cut our dive short while I still have a lot of excess in my tank. For that reason, and only EARLY IN THE DIVE, Peter will go on my long hose for a while. I not only don't think that's dangerous, I think it's a good thing. We get the practice of air-sharing and swimming while sharing gas; both of us have oodles of our own gas, so even if somehow we got separated, there's no problem. And we end up with equalized gas consumption.

We have had problems with DMs seeing us do this (even, sometimes, after we have explained that we are going to) and literally freaking out, and I've had a PADI instructor tell me that he felt it was unconscionable, because once you are sharing gas, the only thing you can do is an immediate ascent. But we're CAVE DIVERS . . . If we share gas, we swim out. I think it's good to practice that.

I agree.

We've had this conversation before. If we break our gas supply down into "reserve/rock bottom" and "useable", we can use the "useable" portion any way we choose. We can breath it, give it away or throw it away and it makes no difference at all because we still have enough to get back.

My wife and I also spend quite a bit of time with one of us on the others long hose just for practice so that it goes smooth should we ever have to share gas for long distances to get out of a cave or wreck.

I don't know where this "the dive is over" stuff comes from.