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Sunday, 16 May 2004 00:00

My Cavern Sinkhole Course

By Keith Jobson


There's a saying that takes on more urgency the older I get - "You only regret what you don't do." The time had finally come to cross off one more potential regret - the Cavern/Sinkhole diving course.

Completing the cavern/sinkhole course and seeing firsthand what everybody raves about in SA's Mt Gambier has been a goal of mine for a number of years. After one false start and another clash of dates I finally got the green light to do the course with CDAA instructor Brian Cornell and "student" instructor Paul Leslie from DIS. Joining me as students were three others, all keen divers with Deep and EANx backgrounds.

Part 1

On a Tuesday night we attended the DIS shop in Ringwood for a night of theory, covering topics such as CDAA history, natural history, equipment considerations, buoyancy and anti-silting, gas management (rule of thirds), decompression, access procedures, dive planning, hazards, and accident analysis. Given the background of the students a fair amount of the theory was almost revision, although the CDAA history and environmental considerations with sinkholes was all new.

Saturday morning we all fronted up at Queenscliff Dive Centre for two days of fun and games. After some more theory covering communications and reel and guideline use, we turned the backyard of QDC into a spider's web - lines going everywhere, tied off to anything and everything. Upturned chairs, railings, door knobs, you name it we tied off on it. Then came the fun part (for the spectators!) where we practiced following that same line back to the beginning (ie. the cave exit) with eyes closed to simulate a silt out. Instantly those upturned chairs and low branches became hazards, with a few bumps and scratches the result. After a couple of hours of drills on how to reel out, tie off or wrap the line, lock and abandon, and the all-important finding our way back with eyes closed we were ready for the pool session.

All of us students have very similar gear configuration - twin cylinders, backplate and wing, 7' hose, canister light - so that made things very quick when reviewing equipment considerations. Streamlining and eliminating entanglement points is a key point in caverns and caves, so get rid of all those danglies if you want to do the course.

QDC have an indoor pool that starts shallow and has a sharp drop to around 3m. This was to be our home for the next few hours. We spent a few minutes getting our buoyancy sorted, as fresh water requires less weight than the ocean. Personally I went from 9lbs on my weight belt to none at all, although I did go back to 6lbs for the pool session due to the extreme shallowness.

In the pool we covered reel use, line placement techniques, reel locking and abandonment, blackout line following and air sharing while following a line. In everything we did we had to demonstrate good buoyancy and anti-silting techniques. The first time I was "silted out" I realised that the value of that tiny piece of 3mm line was infinitely more than what Bunnings charge for it. It is instantly the most important asset you have apart from air; it is literally your lifeline. After many combinations of mask off, blacked out or both, plus out of air drills thrown in for good measure we emerged tired but satisfied. Saturday night saw the typical shenanigans of a group of divers in a local pub, and somehow we all managed to be back in the pool on Sunday morning to do it all again.

The next Tuesday was another theory night at DIS headquarters where we also did the exam. A few pages of multiple choice questions, plus a few pages of written answers. No answers tonight though, that would have to wait until Mt Gambier. Unfortunately tonight we learned that one of our group wouldn't be joining us due to personal reasons, so our two buddy pairs were now one threesome. With gear all sorted, tanks filled, travel logistics organised we departed. Only four more sleeps!

It is a long way to Mt Gambier. Any way you look at it it is 5 - 6 hours from Melbourne. And there is a surprising amount of "stuff" to pack into your car. Two people with all their dive gear and luggage fitted (just) into a standard sedan. In Mt Gambier we were joined by DIS regulars Chappy and Chris, who took the opportunity to do some "pleasure dives" in some of the sinkholes. As it turned out they only dived in two sites, more on that later.... Accompanying Brian was another CDAA instructor, the "world famous" (his words) Stan Bugg who was along to help out Brian and Paul. Their Navara twin cab was packed to the roof. I'm not quite sure how two people can have that much gear to fill the back of a Navara ute - I've taken a family of 5 away for a week and had spare room - but they did it.

Saturday morning we met at Goulden's Hole, a popular training site. A smallish sinkhole that bottoms out around 24m, the water is a reasonable 15 degrees C, with ~5m vis (before we got there!) We spent a couple of minutes checking our buoyancy and trim, and generally heaping pity on the sole wetsuit diver of the group. He took it well, claiming the water wasn't cold at all... (denial?) Chappy and Chris headed off to Little Blue Sinkhole for a dive.

My first impressions of a freshwater sinkhole - dark and eerie. The lack of vegetation was certainly different to the ocean, sort of a "moonscape" atmosphere particularly when the sinkhole started to undercut. Nothing there except me and the yabbies.

Part 2

So into the drills and skills - reel out, tying off and communicating via torch and hand signals, all the while maintaining perfect (!) buoyancy and trim to minimise the silt. And there was no escaping the watchful eye of Paul and Brian. For these drills we buddied up as a twosome, with the third person off with Stan demonstrating finning techniques - modified flutter, frog kick, and helicopter turns. Put those hands away! The drills continued, losing masks, silt outs and out of air scenarios the whole day. Those instructors ought to upgrade their gear, it kept failing at an alarming rate!

At lunch we warmed up a bit (amazing how cold it gets even in a drysuit) while Stan and Brian whipped out their portable compressor to refill their tanks. So that explains *some* of their gear... Over lunch we went over the exams and discussed where we went wrong. A few silly mistakes, but not enough to knock any of us back, so that was good news.

Dive two was again in Gouldens, for more of the above. We were also joined by Chappy and Chris for the afternoon. Another satisfying session, with all our skills becoming more refined as the day progressed. The instructors were happy, and so were we! Back to the motel to dry our undergarments (the arms get wet with all the reel and line work) and our poor wetsuit diver obviously got prime position in front of the heater to dry his wetsuit.

Sunday morning we met at Little Blue Sinkhole. This is the local swimming hole, probably 50 metres diameter and about 39m deep, full of all sorts of rubbish - a car, petrol bowser, old tyres, signposts, trees, everything. It does have fabulous access with steps and a pontoon making entry/exit super easy for divers.

This was a deep dive, and our task here was to plan the dive using tables, calculating turn time, turn pressure with rule-of-thirds, the sequence of our group (who reels out, etc) and also managing a stage cylinder. On this dive the wetsuit diver was no longer the "target", it was me as I was using smaller 7L cylinders and the others twin 12's. Limiting factor = me! Well we'll see - this was also a no-deco dive, so it would either be turned on time or pressure.

Dive planned, slate written up, S-drills completed, we descended the shot line. At around 15m in very murky water we passed through a thermocline with the 15 degree water dropping to a chilly 12 degrees. Our torches made little impact until the bottom suddenly appeared. Diver two clipped off the stage cylinder. I tied off the reel, and off we went into the gloom, tying off on street signs and rocks and branches. We stayed close to the wall as our imposed depth limit of 30m meant there was nothing to tie off to out in the middle (depth 39m). Our turn time was quickly reached (NOT air pressure - woohoo!) so we turned the dive. Back to the shot line we went, simply reeling in the line the way we came. In the murky water the advantages of a line are very apparent - whilst the green glow above always indicated a direct ascent, it is nice to have a sense of position with the line.

Back up the shot we ascended, with diver 3 managing the stage as well, to our planned deco stops. Here is a huge difference and advantage over ocean diving - deco stops are incredibly simple! No surge or swell to muck up your depth, you just hang there effortlessly. On the deco stops our instructor's regs again failed, necessitating donating the long hose. And his way of saying thanks was to make us perform a mask clear! We exited the water right on schedule. On the surface we were debriefed and again the instructors were quite happy at our performance.

Whilst we were on our dive Chappy and Chris also dived at Little Blue. Upon surfacing Chappy realised he had lost the wide angle lens from his camera, somewhere in Little Blue sinkhole.... Guess where they would be diving that afternoon. And the next morning. Search and Recovery anyone?

After lunch we were back at Goulden's Hole for a climbing session. A number of sites at Mt Gambier require access via wire-rope ladders and lowering gear via ropes and slings, so a basic understanding of appropriate techniques and gear is essential. Back in the water we underwent the "stress test", plus in-water gear removal and donning, valve shutdowns, and some more mask off, blacked out, out of air drills for good measure. We slept very soundly that night... I hung out until 8.30, and I think the other 2 were in bed by 9. Very exhausting!

Part 3

Monday morning was the highlight of the weekend. We were booked on the 8am slot at Piccaninnee Ponds, a dive site about 30km south east of Mt Gambier. This is the one I was waiting for: gin-clear water and a spectacular white limestone cavern that apparently rates as one of the best dives in the world. As we geared up we listened to our experienced instructors Stan and Brian who told us all the "back in my day" stories about the site. Stan, with 97 dives at this site alone (I think he helped dig the chasm ;-), noted that he would often arrive at 7am to find cars already there and divers in the water. "If you weren't here by 9am there was no point" as all the early divers had silted the site out. Nowadays at Pics access is controlled, with slots at 8, 11, 2 and 5. Each slot has a strict one hour limit, ie. we had to be out of the water at 9am, which then gives 2 hours for the silt to settle before the next group.

Gearing up is done in a shelter, next to a toilet block, and then it is an easy walk across a boardwalk to a pontoon. All these site improvements are typically done by CDAA volunteers working in conjunction with local councils and landowners. This dive was simply for the "wow" factor - no skills or drills thank goodness!

Dropping off the pontoon into the first pond it is a 50m surface swim across to the chasm. We descended, past the reeds and down a narrow fissure called the "Chasm" to the "Dogleg" at around 36m. This is the CDAA depth limit for this site, as beyond the Dogleg it enters a dark zone, narrow and silty which drops to 100+ metres. Some people have had very lucky escapes from beyond the dogleg (eg. Tom Mount recounts his escape from here in the preface of the IANTD Cave Diving Manual); others have not been so lucky, thus the CDAA limit. Rangers know how to read dive computers, and depth offenders will be reported and banned. Harsh perhaps, however CDAA policies exist for our protection!

Turning back up the Chasm to around 14m we enter the Cathedral. In here our five bright dive torches really get to shine, lighting up the massive white limestone cavern. It is huge, and absolutely beautiful in crystal clear water! With Paul and Brian keeping an eye on their students, we buzzed all through the Cathedral, looking into nooks and crannies and just generally awe-struck at the whole experience. Working our way slowly around the walls of the cathedral we reached the ceiling at -6m. Here it is a simple process to insert a little air in your wing and just lie there held against the ceiling to do the 6m deco stop. After a few minutes watching a freshwater eel we exited the Cathedral, and gently swam back through the clear ponds at 3m effectively doing the 3m deco stop.

Gearing down we all swap superlatives about the dive, quite bubbling about the experience. A short drive to Port MacDonnell for an air fill and a coffee, via Ewens Ponds for a look, and we then headed back to Little Blue for a repeat of yesterdays dive but taking into consideration the repetitive nitrogen. At Little Blue we find an extremely happy Chappy and Chris, who have somehow pulled off the impossible and found the lost camera lens in the silt.

As it turned out the dive plan was exactly the same as yesterday, with the roles changed. I managed the stage cylinder today, and today we managed to travel about twice as far as yesterday in the same time. Obviously our skills are becoming more refined. On this dive one of our instructors "took the opportunity" to give us real- life experience at getting entangled in the line, with it wrapping around his fins straps. No names mentioned as I don't want to ruin the "world famous" reputation!! Back on the surface, we are four happy lads - no longer students but now official Cavern/Sinkhole Divers, and Paul is now a Cavern/Sinkhole Instructor.

So this is what people rave about. I can honestly say this was the most enjoyable and satisfying course I have completed to date. The skills, the sites, and the potential future diving it opens up are just fantastic. The rubbish-filled sinkholes I can take or leave, but Pics is a spectacular dive and will certainly be on my list for future trips. And Kilsbys. And The Shaft. And...