Kevrumbo:
On a 3-man Team, Wreck Night Dive, single-file through a restriction, gas-sharing, lights-out egress Drill with the OOG Diver sandwiched between --that OOG Diver has got to know, or at least have an idea how much gas his initial donor has left to share.
I think that's a different scenario from what everyone else is talking about.
The whole "show the SPG" step (which is no longer taught by GUE) was a kind of "marriage" between two schools of thought regarding gas sharing.
Originally, some of the GUE tech folks were teaching students to show their SPGs, while the cave folks were not. I believe that's because OW diving offers more options for what to do in that situation - for example, do the divers need to begin their ascent right there, or do they have sufficient gas to swim to a more suitable exit point? Checking the available gas helps in the decision process on what to do next. In a cave however, you really only have one option (which is to swim back the way you came), and you either have enough gas to do that, or you don't. Stopping to check the gauge at that point doesn't really tell you anything useful, IMO (speaking as a "primarily cave" diver).
At any rate, when it came time to standardize the curriculum, the cave guys conceded on the "check the SPG" step, as a way of forcing students into a more measured response to the emergency. They were already teaching the cave students to take a few seconds to calm everyone down before exiting, and stopping to check the SPG kind of fulfilled that requirement, so that's what they all agreed to do.
In Kevrumbo's scenario (three person team, restricted passage), I agree that the team needs to evaluate their remaining gas supply before entering the restriction. The currently donating diver needs to be sure that he will exit the restriction with sufficient gas to get him or her the rest of the way out. If sharing gas through the restriction results in too much gas being used from the donor's remaining supply, and if the currently OOG diver can't easily accept air from the third team member while
in the restriction, then they will need to switch donors before entering the restricted area.
At that point, however, it is a
team decision, and not just for the benefit of the diver who is OOG. The currently donating diver will need to have a good idea of how much gas he will need for the exit, and will need to advise the remaining team members that the OOG diver needs to switch. Obviously, the OOG diver will need to know "why" the switch is being made, so checking (and perhaps showing) the gauge makes sense there. Personally, as the OOG diver, I would probably just "know" what was going on there, and trust that my teammate was forcing me to switch donors for a good reason - don't know that I would insist on seeing the gauge at that point, but I don't see any real harm in it either.
For a two person team, it doesn't really matter what you do - if you planned and managed your gas properly, there should be a sufficient amount left to get you both out. If not, then there isn't, and there's not a whole lot that you can do about it at that point. So I don't really see how checking the gauge helps in that situation - if anything, it probably creates even
more stress.
OW diving is a slightly different animal though - if your only option to is to surface immediately (like in the cave scenario), then there's not much point to an SPG check, as far as I can see. However, if an SPG check helps your team with "what to do next", then maybe there is some merit to adding that step.
