Jim

This email is a combination of DIR evangelism and a dive report for those
interested in such things.  Recall your email recently:

>For the benefit of our sometimes doubtful audience, what effect did your 
>rather expensive changeover from strokedom to DIR have on your diving 
>experience?

I usually confine my emails to big issues such as cable ties :-), but it
occurred to me that I had another angle from which to answer to your
question.  Here is a personal account of a dive I did at the weekend.  The
big boys have done bigger dives, but for me the dive below was one of my
most serious and fun dives to date.

This weekend Greg Maud and myself pushed the end of the line at Badgat,
South Africa.  We are both DIR divers and perhaps it was this equipment and
philosophy that helped.  Mike Fowler had hoped to "slip away", whilst is
partner Don Shirley was not watching, and join us on the dive.
Unfortunately, over the weekend the South African Free Diving Championships
were being held and so the IANTD Badgat Dive Centre was busy mixing gas for
support divers.

Badgat is a disused and flooded quarry with an extensive and deep cave
system.  Water temperatures are around 25 Deg C (77 Deg F) in the shallow
deco stop depth.  In the cave, it gets colder but I keep forgetting to check
the temperature.  Badgat is an altitude dive being 900m (2,970') above sea
level.

Outside the cave, there is a pit which is 54m (178') deep and a cave system
in various levels: 9m (30'), 18m (60'), 24m (80'), 38m (125'), 48m (158'),
68m (224'), 108m (356') and beyond.  The entrance to the cave is at 12m
(40').  After spending the weekends of the last two months exploring the
shallower levels with various dive partners, I wanted to check out the 108m
(356') level.

The dive went something like this:

Descend to the cave opening at 12m (40'),  drop to 18m (60') and follow the
permanent line for 130m (429') to the vertical shaft.   We allowed 11
minutes for this portion of the dive as there is a restriction to pass
through.  The swim through murky water at this level was slow but there was
no rush.  We were a few minutes ahead of schedule arriving at the shaft and
hung around to let the clock catch up.

We dropped our 50% deco bottle at the 24m (80') level and dropped down to 36
(119') metres and switched from 35% to our bottom gas 11/59.  Our 35% stage
was dropped here.  Again, ahead of schedule we hung around for a minute,
starting our descent 14 minutes into the dive.  The plan was to reach the
bottom of the shaft at 17 minutes but our descent was slower than expected
and arrived two minutes late at 108 metres (356'), or so.  Must improve this
next time.

Visibility in the shaft and deeper sections of the cave was around 40m, so
it was a great sight to see the bottom loom out of the blackness and the
permanent line beckoning to us to follow.  As we approached the bottom we
glided into swimming mode and started along the line.

The passageways at this level are roughly 3 metres (10') wide and 2-3 (
7-10') metres high.  My primary light illuminated the walls clearly and the
visibility was so good that just blackness loomed in the distance.  We swam
at a comfortable yet fast pace and after about 4 minutes reached the end of
the line, 100 m (330') from the shaft.  What an impressive sight!  To the
left of the main passageway was a large alcove with an opening the size of a
garage door.  This opening lead to a straight shaft descending at 45 degrees
down and retaining the proportions of the opening.  Indications are that
this inclined shaft goes to 150m (495') plus.  However, our plan was to see
if the 108m (356') level ends with a rock slide, as is the case with the
shallower levels, rather than to gratuitously gain depth.

I tied on to the end of the existing line and continued along the
passageway, adding a further 40m (132') to the line, making a total of 140m
(462') from the shaft and 380m (1,254') to the surface.  At the new end of
the line, the passageway just went on and on, confirming that it does indeed
extend under the pit above.  At this point we hit thirds, so I tied off and
we started the swim back, reaching the main shaft 29 minutes into the dive.
I started deep stops at 70m (119') with a slow ascent between stops until I
reached my first "mandatory" stop at 39m (129').  In total, I added 10
minutes of deep stops to the schedule.  Away from the agoraphobic visibility
of the lower levels, the swim through the training murk of the 18m (60')
passageway was slow and relaxing and reminded me of good old Blighty.
(People from the UK say things like this to propagate the myth that UK vis
is poor, thus keeping the excellent wreck diving to themselves!)  I combined
both the 18m (60') and 15m (50') stops during this swim.

We did our final deco on O2 hanging at the exit point, with back gas breaks
which I included as deco.  Total in water time was 151 minutes.

Equipment-wise, I dived twin 12 litre cylinders of 11/59 and 10 litre stages
with 35% and 50%, my oxygen was in a 7 litre, with a 12 litre safety
available.  Sadly, my WKPP scooter which would have been ideal for this dive
is in the UK.

My deco was without problems.  Greg was running a more conservative profile
and had to do unplanned additional time at 6 m due to a previous shoulder
problem which resolved itself after his extended decompression.
Contingency gas was available for this.  My tables were produced with Abyss
2.02 (125 Algorithm, safety parameters set to zero).  Deep stops were not
planned in but executed (added) into the actual profile.  8 minutes of back
gas breaks were counted as part of the deco whilst on O2.  The "mandatory"
deco stops suggested by the Abyss were followed and not shortened.  Greg
used DECOM for his dive planning and, as mentioned earlier, had a profile
more conservative by 23 minutes.

Thanks to Mike Fowler and George Leonard for mixing the gas at this busy
time.  Thanks also to Lo Vingerling for in-water support.  Mike
"if-only-I-could-get-the-Halcyon-though-the-green-door" Fowler, was a bit
miffed at not being able to join us, as planned, but this was his most busy
weekend of the year.  We originally had planned to do the dive with a stage
of bottom gas to increase our bottom time.  However, I must confess that on
the dive of the previous day I found that I had a leaky dry suit and could
not guarantee it would not leak on the day of the "big" dive.  I didn't
fancy 3-4 hours being wet in water, so we adjusted our dive plan.  Perhaps
we would have got to the end of this level?  I only hope I have an
opportunity to find out!

After the dive, I was fortunate enough to I met one of the divers who had
placed the original line three years ago.  I'm not sure what equipment they
used but as I understand Heliair (50/50) was used on the dive.  This has an
END of 50m.  The old line was placed over two dives.  Hmmm.

Now the nub of all of this, referring back to the DIR equipment
configuration aspects, is that we adopted a DIR philosophy and added 40%
more line in our first dive.   This dive was fun.  Although I was excited
during the dive, I remained very relaxed as is illustrated by my RMV which
was just over 13 litres/minute (0.47 CuFt) except for O2 which was
considerably lower.  Our equipment and configuration allowed us to enjoy the
dive rather than worrying about extraneous matters or being numbed by
narcosis.

David Shimell
Project Manager, Sequent Computer Systems Ltd., Sandton, South Africa.
Email: shimell@se*.co* <mailto:shimell@se*.co*> 
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