Thank you for posting ... some additional things to think about, if I may ...
The groups main organizer and leader, apparently had very extensive dive experience (including underwater engineering jobs) and regularly logs an impressive number of dives, and acts as the local dealer for two foreign equipment manufacturers.
Thus, I assumed that the dives would be organized in competent manner and the group members would be competent divers and dive buddies.
This is my mistake number 1. Assumption.
I think it was more putting your trust in someone who had greater experience. The takeaway is that you should always be at least familiar with, if not actively participating in your dive plan ... this helps minimize the potential for surprises once the dive begins.
... the "instructor" made public an incident during which he became so absorbed in the underwater objective of clearing away nets and fishing line that he ran out of no-decompression time and entered into decompression obligation, at a depth greater than 100 feet :reaper:.
In and of itself, exceeding NDL's on a mission-specific dive isn't a red flag. Doing so with team members who are ill-equipped to handle it would be, however ... particularly if the understanding is that the team will be descending, working, and ascending together.
Other divers of the group, also made public, and jocularly, how their dive computers had "malfunctioned" by locking them out of diving for 48 hours, assuming for running out of no-decompression time and omitting required decompression stops :reaper:.
So, on that one particular dive, it can be inferred that several divers in the group had entered decompression.
That would cause me to start thinking about the wisdom of going on the dive with these fellows. Exceeding NDL isn't a big whoop ... not honoring your deco obligation can be ... joking around about it definitely would make me question whether or not they're taking the risks of the dive too lightly ... in which case I don't want to be in the water with them.
Next, on with the dive incident. The "instructor" presented a briefing, noting the local hazards, the geography, and that the pairs must begin the return journey with no less than 700 PSI of gas remaining. So far so good, I think to myself.
How did he arrive at that number? Given the dive profile, that's not adequate gas reserves ... depending on your consumption rate, it's barely adequate to get yourself to the surface, much less have anything in reserve for a potential buddy failure.
Everything pre-dive did not generally ring any alarm bells, but troubles began almost immediately after entry.
From what you've described so far, your troubles began well before the dive did ... you just didn't recognize the signs.
Then, on with the descent, keeping the "buddy" in my view, never more than several feet ahead of me. The way down takes us to a depth around 100 feet (30 meters). My pressure gauge reading approximately 150 bar (likely due to the rapid gas consumption near the surface, and stress), on beginning the descent.
"Ok" I think to myself "I will alert my buddy of the need to cut our bottom time short, no need to abort yet", so I continue the dive.
No alarm bells yet. As long as my buddy and I abort and ascend together, cutting our bottom time short, there should be no problem.
Ah, but as you discovered, there was a problem ... and that problem probably began right here ... with your decision to descend. Depending on the size and type of cylinder you were using, you may well have had an inadequate supply to even consider going that deep ... in which case you should have thumbed the dive before it began.
Dives such as this one point to the value of at least being able to conceptualize how to evaluate your gas needs prior to the dive, rather than watching your gauge and aborting at a certain point ... it keeps you from sliding down the slippery slope of what Lynne referred to as the "incident pit". Please consider reading this article ...
NWGratefulDiver.com
Swimming to and alerting my "buddy" by poking his upper arm (making fully sure that I had his attention), I signal that my gas supply was dwindling, assuming that it was understood that our bottom time would have to be cut short.
He shrugs off the issue, making no eye contact ...
Not knowing what signals were used, I should ask ... are you sure he understood what you were trying to tell him? Did the two of you review signals prior to the dive to assure you would be able to understand each other? You should have.
Now, down at a depth of 100+ feet (32 meters), with my gas supply dwindling, the "buddy" completely oblivious, I sensed an impending drowning at depth, or a dangerous, very fast ascent to the surface should I remain at depth and consume my remaining gas.
Major alarm bells sound off :furious:.
You are now well down the incident pit, and stress is beginning to control your dive plan ... a sense of impending doom is never good underwater, as it causes you to start making irrational decisions.
Quick thinking, abandoning the "buddy", I decide for a controlled solo ascent and back to the point of entry with approximately 800 PSI remaining as I begin the return journey.
As I begin my ascent, seeing my "buddy" several meters directly below me, I attempt at getting his attention by shaking my underwater signaling device, to no avail.
A better plan would've been to tap him, point to yourself, thumb up, and begin your ascent ... in other words, communicate your intent to surface first, then begin your ascent.
We never discussed the use of my signaling device, pre-dive. My mistake number 3, not having discussed signaling devices.
Sounds like you didn't discuss much of anything pertinent to diving as a buddy team ... like the expectation that you descend and ascend together. It's important to discuss expectations and communication protocols prior to the dive ... since you can't really talk about them once you're underwater.
"Sure, you are now one person to avoid like the plague." I think to myself.
... but for all you know he's down there thinking you just abandoned him, and thinking exactly the same thing about you. Messages sent are not always the same as messages received ... this is why talking about expectations and communication protocols are so important prior to the dive.
I continue my ascent, carefully monitoring my ascent rate to be at the slowest visible "bar" on my computer.
Having sketched a map of the area and noting the directional bearings on my slate during the pre-dive briefing, I use my compass to note the direction back to the shoreline and swim for the bearing.
The ascent from 100 feet (30 meters) to 60 feet (20 meters) , to 30 feet (10 meters) is thankfully uneventful, the large group of divers' bubbles visible.
By reaching approximately 60 feet, my remaining pressure shows less than 600 PSI remaining.
It sounds like you didn't make a direct ascent ... but rather angled (swimming in that direction) toward shore. Is that correct? If so, did you consider that with a low air reserve this may not have been a prudent thing to do? Priority one is reaching the surface before you run out of air ... preferably with adequate reserves to inflate your BCD and hopefully a bit more to breathe in case you run into problems getting back to shore.
Still breathing rapidly (probably from stress), and adjusting my NEW weight belt, momentarily neglecting to vent air from my BCD, and losing control of my buoyancy at less than 30 feet and with my pressure gauge showing less than 500 PSI remaining.
Gaining positive buoyancy, my computer showing 4, 3, 2.2
meters and alerting me to descend below the "CEILING".
Quickly venting air from my BCD and descending back down to 15 feet, 5 meters for the now MANDATORY safety stop (due to exceeding the maximum ascent rate), as dictated by my computer.
No ... if you had a ceiling it's because you exceeded NDL ... not because of your ascent rate. And in any case, once you're getting that low on gas you should be heading to the surface. Prioritize your risks ... DCS is fixable ... drowning, much less so.
This is my mistake number 4, momentarily losing control of buoyancy, contributed by not having familiarized with my weight belt.
... and probably a few other reasons ... like a stress-induced change in breathing pattern and dealing with circumstances you're not familiar with.
For some background information, here in Taiwan, news stories have reported cases of divers ascending then dying from collisions with boat propellers. The injuries sustained are massive and blood loss is extremely rapid, insuring near-certain death.
The good news is that motorized boats are noisy, and noise carries extremely well underwater. Listen for motors ... I assure you that you'll hear them long before they can damage you.
I definitely wanted to avoid that possibility, so I made certain that I did not ascend to the surface, and scanned and listened 360 degrees for signs of boats. Very fortunately, there were no sign of any boats or other watercraft.
At this point, I decide to ascend to the surface opposed to swimming to the point of entry, as per my compass bearing, as my pressure gauge showed less than 100 PSI remaining.
You stayed down too long ... 100 psi is well outside the margin of error for an analog pressure gauge. What would you have done if you went to breathe and suddenly couldn't? When was the last time you practiced a CESA and manual inflate of your BCD? If it's been a while, consider practicing this skill.
There were no boats and other watercraft near the area during the time at the surface and the surface swim, but I decide to take a step to warn passing boaters of my presence below the surface. I unclip my finger spool and remove my SMB from its bag, and clip it to the line. Noting not to remove my primary regulator from my mouth, I use my octopus to blast air into the end of my SMB.
Using the last bit of your precious air supply ... next time consider exhaling into it instead.
As this is the first time deploying the SMB, I had not used enough air to fully inflate the entire length of my safety sausage, only about a 1 foot length stuck above the surface.
... another skill that needs practicing ... doing something like this for the first time shouldn't be happening at the time you need it ... your brain's already too overloaded dealing with other issues. I'd recommend practicing this skill on a safe, shallow dive till you're completely comfortable with it.
Maintaining buoyancy while filling the SMB is tricky, to not be dragged up by the extra buoyancy.
Actually it's simple if you breathe into the bag ... transferring air from your lungs to your bag doesn't change your buoyancy at all.
This is my mistake number 4, never having practiced deploying the SMB.
Yes ... great to see that you recognize this ... apply it to other skills you haven't used or haven't practice in a while ... when you need them isn't the time to be figuring it out.
Slowly ascending as I wind in the line back to my finger spool, and stopping for the safety stop, the ascent proceeds uneventfully until somehow, the finger spool had come undone with the metal clip.
I break the surface, I am about 200 feet (70 meters) from the point of entry, marked by a small inflatable dive flag.
I unclip the SMB and roll up the line on the finger spool. Somehow, the line had not fully "clipped".
Peeking below the surface, I see my finger spool slowing descent to the depths, line still attached and attached to the metal clip in my hand.
I could wind the line in by hand, risking entanglement in my own line, in my own gear at the surface, or, I could descend to go for my spool.
I opted against both options, cutting the line, donating my finger spool and line to its next owner.
... or you could have just let it dangle down there, hold the line in your hand, and swim for shore ... towing the spool and pulling it in once you reached shore.
What stands between me and the safety of shore is a surface swim, somehow hampered by stress and the drag on my inflated BCD, for which I considered ditching my weight belt, but did not.
Once again, just flip over on your back ... turning your tank into a keel and getting the weight of it underneath you ... and kick. You'll be amazed how far you can go that way ...
In retrospect, several warning signs were present before the dive.
I was using a piece of NEW equipment (and a critical piece) which I was unfamiliar with: weight belts instead of the BCD integrated weights which I had been doing essentially all of my dives with.
Never having practiced deploying my SMB, I was depending on more luck than I should in having it function and being able to deploy it.
At the shore, even before wetting my toes, the insta-buddy who I was paired with appeared to see me as a unnecessary inconvenience to his dive. There was no discussion of the dive plan, our buddy plan, and any contingency plans. Clearly, he had fully intended on carrying out the dive essentially solo.
... that's probably the biggest flag you missed right there. Learn to cultivate conversations with that "little voice" inside your head that says something's not right ... and if it seems to be not right, accept that it isn't right and don't go. The best accident prevention is recognizing when something's not right and, if you can't fix it before the dive, deciding not to do the dive.
No problem ever got better by submerging it in water.
After surfacing, I opt to sit out the planned second dive, enduring some strange looks and not-so-kind glances by the other divers in the group. I enjoy diving, so this was a slightly challenging decision.
It's a hard choice ... but good on you for making it.
Seems to me there were a lot of lessons coming out of this one dive. Glad to see that you're taking them to heart ... not everyone does.
Safe diving on future ventures ...
... Bob (Grateful Diver)
