Just thought I'd throw out one of my most interesting episodes, which I can look back at now with a wry grin.
This happened just after my OW cert. I am now much more experienced and, hopefully, wiser.
- Dive #6; 2nd non-course OW dive ever (on dive #5, I played around a dock in 30ft of water)
We dove the HMCS Cape Breton: a 400ft navy ship near Nanaimo, British Columbia. Cold water, fair visibility (30 ft), deck at ~90ft, bottom at ~140ft. Moderate current. Group of 3. The other 2 are divers with a fair bit of experience, and have great air consumption. Although I didn't do badly on air during my OW course, you may imagine that being at depth, in current, on a sunken ship (not a sight one is otherwise used to) destroyed any breath control I thought I had.
There are several floats marking various points on the ship. We moored the boat to the middle float and descended the same line, onto the superstructure. I had no problems descending and no problems with narcosis (I think...somehow the memory is a little hazy :11: ). It was a great dive. Until...
After about 15 min at the bottom, and after going down to ~130 ft and then cruising about at 90 ft or so, I had given my poor little AL80 quite a thrashing and was low on air: 700 psi or so. I checked air compulsively throughout the dive, and signaled my buddies when I reached this arbitrary self-imposed limit. I figured I had to ascend, especially since I needed to make a safety stop.
I was getting paranoid at this point and decided that I'd better make my way up. So up I went. Rather suddenly, and alone. I did a pretty nice (if I say so myself) no-reference stop at 15 ft for 5 min or so, breathed my tank down to what I figured was near the probable error in the gauge (100 psi), and then surfaced. A minute or so later, buddy #1 surfaced a little ways from me; she'd followed me up once she realized that I took off on my own. The other buddy made his way back to the buoy line and ascended properly, next to the boat. We, however, were about 50 yards down-current from the empty boat (empty, because we were the sole occupants). After a lengthy surface swim we finally all ended up back on board, luckily none the worse for wear.
*****
Obviously, in hindsight, I should not have done this dive. I thought that my skills at that point were adequate for a dive to this depth, and it probably seemed that way to my buddies as well. BUT:
- My air consumption was much too high to make a safe dive to this depth.
- I was not relaxed (how could I be?; there goes the air consumption)
- I was task-loaded to the limit simply by having to consciously think about buoyancy, depth, breathing, drysuit & bcd management, etc, etc. I did these things well enough but there was no brain-space left for dealing with the unexpected.
- I had no experience diving on wrecks, from a boat or in current.
- I didn't realize what I was missing, so I didn't ask for any clarification during dive planning. When you're an experienced diver making a relatively routine dive, it's easy to skip over the 'obvious' things when planning, like ascent procedures, turn pressures, signals, etc.
So, I didn't realize the potential consequenses of making a free ascent in current, I didn't consider how turn pressures vary with depth, and I didn't realize, at that point, that an ascent from depth constitutes a significant portion of any dive. At that stage, to me, the dive was pretty much over at the point that I started to ascend. And since my dive was 'over', why stick with everyone else? They still had air left. :11:
Needless to say, I learned a lot from this dive. But, it would have been better to learn these things gradually over a course of 50 dives rather than 2.
I would suggest to new(ish) divers that even though you may have adequate dive 'skills' to do a dive, they are NOT sufficient to safely go through with a dive. You must build experience, and gradually learn diving-specific common sense. Your dive buddies can assess and confirm your skills, but they don't know where the limits of your judgment are. And the problem with judgment and experience often is that you don't know you're missing it until you after needed it.
Also, there's a difference between being able to do something well under ideal conditions, and being able to do it at all when things get busy or go wrong. If you have to THINK about a dive skill before doing it well (buoyancy, for example), then you haven't learned it well enough yet.
Some PADI rules/recommendations (ie, OW = 60ft max) might exist for a reason beyond profit! At least, for the first few (dozen) dives. If you think you can bend/modify/disregard suggestions and rules, make sure your own (as well as your buddies') judgment and experience backs up your decision.
Cheers!
