We were watching our air pressure and using the 1/3 example, signaled the DM at a proper point to turn and go back. (I still will work on this as it seems we were still too lax on this.)
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tt5five: FYI, there are lots of situations in which using the rule-of-thirds for gas planning might be too conservative or not conservative enough for a recreational diver. You really need to take logistical and environmental factors into consideration. In this case, significant current was present so padding your gas numbers would be appropriate and using techniques to deal with the current (remain on the sheltered side of the wreck, begin dive into the current, don't stray far from the ascent line, etc.) might have helped. It can be difficult to do all of this if the DM is leading the group without taking these things into consideration.
Our biggest mistake was continuing to follow the DM. (He was a very experienced DM with lots of dives and lots of certifications hanging on the wall. Instilled a lot of confidence in the earlier dives.) In showing the DM our numbers and signaling a desire to surface, we were urged to proceed. I assumed we were just about to turn around and this experience DM knew what he was doing. (I Know what happens when you assume.) It was a DM in Baja Mexico and we will not be returning. I can say that the dives before and after were great. Thanks again for all the comments and education, and not being too hard on a new diver.
First of all, experience doesn't necessarily ensure good judgment.
Perhaps the DM should have instructed you to ascend earlier.
In the DM's defense, perhaps he was operating under the assumption that you were a certified diver and were responsible for your own gas management.
I'm not sure if I would cite this incident as reason not to patronize a particular dive op. Nevertheless, there really should have been some discussion in the form of a post-dive debriefing about what went wrong and how to avoid such situations in the future. Usually such a post-dive debriefing is facilitated by the diver with the most experience and training. Since the DM was in a position of authority, it would make sense for him/her to lead the debrief.
For the sake of completeness, if we are looking for parties to blame, it wouldn't be unreasonable to include your OW instructor in the conversation. One of the most important things a scuba instructor can teach a student is to dive within the student's training and experience. Abdicating responsibility for one's gas management presumably goes against the training your instructor provided.
I'm really glad that things turned out well for everyone involved. Following the DM blindly is something that many divers are guilty of, so you're definitely in good company. I remember my first warm water dive vacation in Cozumel several years ago. The DM was leading our group of relatively inexperienced divers through a series of short swim-throughs. Sounds like fun, right? Well, a couple of the divers sustained injuries from a loss of buoyancy control inside the swim-throughs. One guy suffered a head wound that bled fairly impressively. I was definitely guilty of following the DM blindly through the swim-throughs. After the guy cut his head open, I reassessed what I was doing and realized that I didn't
need to do the swim-throughs -- my buddy and I could simply wait for the group to exit on the other side. Those dives became a lot less stressful and more enjoyable. I didn't have to go through a cloud of silt that the diver in front of me kicked up inside the swim-through. I found that when I wasn't so focused with navigating the swim-through, I could pay more attention to the larger aquatic critters (spotted eagle rays, sharks, etc.) which swam by on the outside of the reef.