a hypothetical for discussion

[FW]

...I just did a dive in Ginnie ....

Did you get a chance to test the new camera?

PS, I am glad you made it out OK. It does show that some people aren't using nearly enough bailout

[Sludge]

i was more interested in the routes & reasonings people would choose.

Okay. Go to Olson. No other option would be considered.

A diver new to the Peacock system may choose one of the other options, but I have almost a hundred dives there, and I've studied the map since I was a cavern diver.

While we're at it, I've always had a problem with "the thumb." People reach thirds and "give the thumb." But the thumb and the finger twirl mean two different things, and I make sure everyone I dive with knows the difference.

The finger twirl means to turn around. No emergency, just turn around and go out about the same as you had come in. If you lolligagged on the way in, you can lolligag on the way out (although not quite as much lolligagging should happen on the way out).

A thumb means "leave now." Although not necessarily a full-fledged emergency, there's no wasting time getting out. It usually means the diver is not 100% comfortable and wants to be at the surface without much delay.

Systems such as Jackson Blue, with one and only one exit, mean go straight out without delay. Systems such as Peacock mean an alternate exit might be considered. But within reason. If we're a little closer to Olson than Peacock 1 and I get a thumb, we're still exiting where we came in. But in your example, where you KNOW you're way closer to Olson than Peacock 1, we're coming out Olson.

[KarsticGator]

It's a long story why, involving some restrictions that took longer to get past than I was expecting, an unintended jump and a flooded rebreather... but that's exactly the sort of hellish scenario that reserves are designed for. An even more amazing statistic - of those 300 cu ft used, I used 200 cu ft "navigating" (poorly, with a very screwed up head) from 4800 ft back to 3200 ft.. THe next 100 cu ft got me to the exit - and even that was due to a ridiculous SAC rate under pressure.

I'd be interested in hearing more details regarding this dive... if you don't mind sharing them. (Purely from a curiosity standpoint and not from a critical one.)

[FW]

.... Systems such as Peacock mean an alternate exit might be considered. But within reason. If we're a little closer to Olson than Peacock 1 and I get a thumb, we're still exiting where we came in. But in your example, where you KNOW you're way closer to Olson than Peacock 1, we're coming out Olson.

Another "forgotten" hand signal is the thumb, and index finger. It is usually used to mean "that way is out". I would hope nobody would ever need to ask that. In the above senario it could be used to say I need to go out fast, and Olsen is closer. It could also be used to say I want to leave now, but I have gas to get back to P1 without delay.

FWIW, I tried that signal with the buddy that was trying to go the wrong direction, but she didn't seem to understand it.

[Gary]

I recall reading about an incident in one of Sheck's books where there was a sudden complete gas loss at maximum penetration and he and his buddy barely made it back to their stage bottles and out alive. While this is a rare event, it's enough for me to not ever push air management all the way to 1/3s.

Actually that is one of my favoite stories - one that actually does show how independent/sidemount advantage over manifold (the gas loss from both tanks was only posiable due to the manifold).

But IIRC while they were at "maximum penetration" they had turned early on gas. They had more than thirds but ran out before reaching stages (due to bouyancy issues and air sharing). Even after reaching stages they nearly ran out of gas again even though they both had full supplies at that point.

If they had been at thirds when the the accident happened they almost certainly would not have made it. While if they were diving independents/sidemount it would have been a non-event - not even a story worth including.

[RN]

He's here...

I just did a dive in Ginnie on CC where I reserved 400 cubic feet to travel 4800 feet. I made it out with under 100 cubic feet left. In theory, I used about 3 times the amount of gas that I should have. It's a long story why, involving some restrictions that took longer to get past than I was expecting, an unintended jump and a flooded rebreather... but that's exactly the sort of hellish scenario that reserves are designed for. An even more amazing statistic - of those 300 cu ft used, I used 200 cu ft "navigating" (poorly, with a very screwed up head) from 4800 ft back to 3200 ft.. THe next 100 cu ft got me to the exit - and even that was due to a ridiculous SAC rate under pressure.

Let me emphasise this - if I had dived with only double the gas theoretically needed to exit, I would have run out somewhere around the Henkel, and drowned. If I had dived with triple the reserves, I would have barely made it. I NEEDED a 4x reserve.

My (somewhat misunderstood) philosophy is to a) work out the bare minimum needed to exit, and b) add whopping reserves onto that bare minimum. In this case, I had 4x the reserves theoretically needed (or, in OC terms, I was diving fifths) and it was nearly not enough.

Ah, the naughty word censors... doo-dah happens. Prepare for it.

BD, I think what a lot of people are telling you is that it's not a matter of routes, its a matter of never going anywhere near thirds in a low flow scenario like Peacock. SPG errors are one of many very good reasons NOT to go to thirds.

Thanks for this great example of why 1/3s is not enough!!!

While we're at it, I've always had a problem with "the thumb." People reach thirds and "give the thumb." But the thumb and the finger twirl mean two different things, and I make sure everyone I dive with knows the difference.

The finger twirl means to turn around. No emergency, just turn around and go out about the same as you had come in. If you lolligagged on the way in, you can lolligag on the way out (although not quite as much lolligagging should happen on the way out).

A thumb means "leave now." Although not necessarily a full-fledged emergency, there's no wasting time getting out. It usually means the diver is not 100% comfortable and wants to be at the surface without much delay.

Exactly!!! I teach my students about this difference. My first sidemount passage in JB had me coming back in zero visibility. I came up to the restriction and hit rock. I backed up and changed direction again, and hit rock again. This happened 3 times before I found the hole I was looking for. Keep in mind I had the line in my hand the entire time! When I popped out I signaled my wife with the thumb. Our usual exit consists of learning what the cave looks like from that direction and also looking for side passages for future dives. We still always get out with close to 2000psi. Well, she proceeded to do this. I signaled a thumb again and she signaled back and continued a leisurely pace out. I finally got in her face and signaled one more time. She got it that time. Once back at the surface we decided a twirly finger is the signal for a leisurely exit and a thumb means it's time to GTFO. Unfortunately, there are divers out there that think the thumb is the only appropriate turn signal, instructors included.

Actually that is one of my favoite stories - one that actually does show how independent/sidemount advantage over manifold (the gas loss from both tanks was only posiable due to the manifold).

But IIRC while they were at "maximum penetration" they had turned early on gas. They had more than thirds but ran out before reaching stages (due to bouyancy issues and air sharing). Even after reaching stages they nearly ran out of gas again even though they both had full supplies at that point.

If they had been at thirds when the the accident happened they almost certainly would not have made it. While if they were diving independents/sidemount it would have been a non-event - not even a story worth including.

It's been years since I read the account. Thanks for the clarification. It brings across the point even better!

[aainslie]

I'd be interested in hearing more details regarding this dive... if you don't mind sharing them. (Purely from a curiosity standpoint and not from a critical one.)

I've offered it as an NACD article. We'll see if they want to publish it. if not I'll put it up here. Give me a couple of weeks on this one.

[Bobby]

Exactly!!! I teach my students about this difference. My first sidemount passage in JB had me coming back in zero visibility. I came up to the restriction and hit rock. I backed up and changed direction again, and hit rock again. This happened 3 times before I found the hole I was looking for. Keep in mind I had the line in my hand the entire time! When I popped out I signaled my wife with the thumb. Our usual exit consists of learning what the cave looks like from that direction and also looking for side passages for future dives. We still always get out with close to 2000psi. Well, she proceeded to do this. I signaled a thumb again and she signaled back and continued a leisurely pace out. I finally got in her face and signaled one more time. She got it that time. Once back at the surface we decided a twirly finger is the signal for a leisurely exit and a thumb means it's time to GTFO. Unfortunately, there are divers out there that think the thumb is the only appropriate turn signal, instructors included.

I use the same signals and learned an important lesson on a dive with regular team members. We had been diving for a few days with the same group of people. On this day another of our regulars joined us fresh out of a class (Apprentice IIRC). We were a little complacent in our dive planning and did not go over the finger swirl and thumb signals. The diver out of the class gave the thumb signal and was questioned to ensure he meant thumb. In his class they had only used the thumb to turn the dives and he had forgotten about the finger twirl. This resulted in added stress for everyone in the team with each of us wondering who was having a problem and what it was. We all made mistakes that day and allowed complacency to enter our diving from familiarity of us diving together.

Bobby

[DA Aquamaster]

A large part of the thumb versus twirly finger problem is cultural.

How many times do you hear people say "we thumbed the dive" when talking about a normal "turned the dive" situation? "Thumbing" a dive has become common slang for turning the dive and as such has lost much of its original meaning and all of it's distinction as an "EXIT NOW ASAP" signal. We all play a part in correcting or continuing that misperception of the signal by our actions in either clarifying it, or not, when we see it and hear it.

I don't think we have to reserve the thumb for full on emergencies, by any means, but it should clearly convey a "we need to leave right now and proceed out with no dicking around" message.

[LCF]

I like the "twirl" for turn and thumb for get the heck out of Dodge, but I have been specifically taught not to use the two different signals. It seems as though there ought to be some easy way for a diver to convey an urgent exit, though. Although most problems will be apparent to the team, some may not be, and specifically any relating to an individual diver's physical state.