“The Great Blue Hole” located on Lighthouse Reef, an atoll approximately 50 miles east of Belize in Central America is an incredible place to see…and dive. It is the water-bound equivalent to the Acropolis in grandeur and immensity. In 1970 the late Jacques Cousteau explored this natural wonder with two one man submersibles and some relatively shallow diving on scuba. The resulting TV episode became one of the most popular broadcasts of it time.
In 1995, an international group of divers under the Cambrian Foundation banner became the first open circuit divers to touch the bottom, exploring and bringing back descriptions of the 408 foot deep part of the formation. The Cambrian Foundation is a not-for-profit organization dedicated to the Research, education and preservation of aquatic resources.
In 1997 Bret Gilliam put Dr. Robert Dill (head geologist for the Cousteau expedition) in touch with The Cambrian Foundation to discuss his interest in how these deep diving techniques could be of assistance to marine geologists. During the 27 years since the first Blue Hole expedition, new analytical techniques and instruments had been developed that would permit the dating and determining of the chemical nature of speliothems. These dates and isotopic values could be used to determine important historical changes in the world’s oceans as they filled with water stored on land in the vast continental ice sheets following the last ice ages.
An expedition was scheduled for June 1997 to continue the work Dr. Dill had started in 1970. The 20+ member Expedition team (Including Dr.Dill and his associates) would be based at the luxurious Lighthouse Reef Resort on a gracious invitation from Walt Walters and the management staff of the resort. After performing the logistical tightrope walk of getting all the people, equipment, gas and boats together on this small, quiet island, the objectives were set forth:
- With permission from the Belizian government we were to obtain geologic samples from various depths to provide scientists with one-of-a-kind specimens for establishing a time line for the rising sea levels following the previous ice ages.
- To obtain core samples of the sediment on the bottom of the Blue Hole
- Explore potential cave systems leading to or from the Blue Hole
- Acquire a complete video record of the entire project.
One of the divers on this expedition was Andreas (Matt) Matthes, fondly known as ‘The German’. He is originally from Braunschweig, Germany and currently lives and teaches cave diving in Akumal, Mexico. It is from his unique outlook (not to mention his logbook) that this story is being told.
The First Day (June 2, 1997)
We spend the day oxygen-cleaning the tanks and valves needed for our partial pressure blending method. The steel tanks which were brought from the US are assembled into double configurations. Lighthouse Reef Resort has more than 100 aluminum 80 cu.ft. tanks, of those, we O2 clean about 40 to be assembled as doubles for the safety divers, the film crew and the rest rigged for stage bottles. All of the valves are changed to DIN valves. The yoke valves are not safe enough for the dives we are planning.
In the evening, for the first time, the whole expedition team assembles in one of the spacious bungalows donated by Lighthouse Reef Resort to introduce everybody. I know about a third of the team members from previous projects. Goals of this expedition are explained. Since this is a true scientific expedition, the geologists tell us where we dive, where to take samples, what to document and where to take the core samples. . .
The physicians will try to validate our deco software while doing Doppler tests over a period of 5-6 hours after every mixed-gas dive and looking for bacteria prone to grow in PO2 rich regulators.
The two big Bauer compressors of the resort run in line late at night to fill and blend all the tanks necessary for the dive tomorrow. Until after midnight the compressors can be heard on the otherwise perfectly quiet tropical island.
The Second Day
Begins very early. It takes a couple of hours to transfer all the equipment from the filling area down to the dock and onto Frenchie’s boat. Terrence and I are the first divers out of this year’s expedition to return to the bottom of the Blue Hole. On the boat are the film crew, The geologists Dr. Robert Dill and Dr. Tony Jones. The physicians Dr. Clyde Martin and Dr. Andrew Pitkin who will conduct Doppler tests directly after the mixed-gas dive to check for inert gas bubbles in our bloodstreams, to find out how safe our deco profiles are with the Pro Planner decompression software.
Bottom mix is an 11/60 trimix, since we know from the last that the depths are around 410 feet. On board there are three safety divers who can assist us in case some unforeseen thing happens with our deco gas supply. The dive plan is to switch back from bottom mix to air at a depth of 220 feet, then switch to EAN 40 at a depth of 100 feet and finally, spend the shallow 20 and 15 foot stops on 100% oxygen.
A tri-pack with bottom mix is on my back (double 108s with a 45 cu.ft. bailout between them) and a single 80 cu.ft. stage bottle on the left and one on the right with air and EAN40 respectively (our safety divers were staging the oxygen tanks at 30 feet). We wait for our safety divers, Kyle Creamer and Chris Johnson, to get in the water and put the O2 tanks in place. Just before the descent, with closed eyes, I go slowly through the dive, visualizing every phase of the dive with all hand signals and gas changes. After a while Terrence is looking over to me and with a short nod he signals me that he is ready. So am I. The descent begins.
Down until the depth of about 150 feet the water is relatively warm. There a thermocline is refreshing us. The visibility clears up to an incredible 150+ feet below the 150 foot level.
Along the south wall of the Blue Hole at a depth of about 155 feet stretches a big grotto with giant stalactites. At 220 feet, we level off to conduct our gas switch. The helium mixture is easier to breathe due to the lesser density. A quick hand signal and we continue our descent toward the darker water layers below us.
The dark blue changes first to a dark gray-blue then to black. At the depth of about 300 feet we hit a hydrogen sulfide layer and the visibility drops down to a couple of feet. The sulfur smell is very clear. With the downline from the reel we dropped before the dive in one hand, my 50 watt lighthead in the other, we drop slowly through the H2S layer. The visibility below the layer clears up to about 100-120 feet at the depth of 350 feet. The bottom comes into view – light brown silty sediments. It is flat toward the center of the Blue Hole, but toward the wall, the falling sediments formed a kind of dune directly below the rim. A quick partner check and with the help of a compass we swim over the dune toward the wall, under a giant overhang which prevents a direct ascent to the surface. At our maximum depth of 360 feet the rock looks like white Swiss cheese. It reminds me of the rock in the Mexican caves I dive regularly. I feel so small in this giant hole in the ground, like an ant in a bowl, it is so huge.
After a 20 minute run time the up signal is given and we start our slow ascent back to the surface. Unfortunately we couldn’t localize any stalactite or stalagmite on the bottom/wall junction for our geologists.
The downline is now permanently installed. Along it we ascend to a depth of 220 feet to commence our switch from bottom trimix to air. One of our safety divers is already waiting there for us, asking about our gas supply status and well being. Everything OK.
The visibility is very good. At different depths, divers are to be seen, busy with filming or geological studies. The stalactites in the grotto are of immense size. Only when a diver gets close to one is the real size seen. A diver can completely disappear behind one of those giants. The rim and the boat can be seen from 200 feet of water. The first decompression stops are short. At 100 feet we do our gas switch to EAN40, the deco stops becoming longer and longer the shallower we ascend.
At 20 feet we do our gas switch to 100% oxygen to maximize our off-gassing process. Laying in the sand on the Blue Hole rim make this dive one of the easiest to decompress on. Little colorful fishes entertain us in the rather boring process of decompressing after a long, deep mixed gas dive. Laying there on the sand I have lots of time to think about how grateful I should be to do this kind of diving in times where people have been walking on the moon, climbing the tallest mountains of our planet, walking to the poles and kayaking through the Amazon. In times where one should think that there have been people everywhere, that everything on this planet is explored, there are still areas where nobody has been before and that you can be the first. That is an awesome feeling.
After 3+ hours of decompression it is time to ascend back to the surface. The rest of the expedition team is waiting with a snack for us, something I really need right now, and lots of water to rehydrate. Just out of my wetsuit, Dr. Pitkin begins with his Doppler testing. Only a low grade bubble score after squatting is all there is to hear. The readings are recorded on a DAT recorder for later analysis by specialists in England.
On the boat ride back to Lighthouse Reef Resort I still have to think about the dive – the magical Blue Hole has got to me. The next two weeks of diving are looking promising.
The evening is full of activities to get the equipment ready and to blend the breathing gases for the next diving day. Getting the gear down to the pier close to the boat, maintenance, calculation of gas volumes and dive profiles and their transfer to slates take a good amount of time.
Meetings with the geologists who lay out the plan and goals for the next day depend on our findings on a day to day basis. There are also the continuing Doppler tests for hours to come and the safety divers calculate and rig the needed spare gas and tanks.
Something like this, in the dimensions we are conducting our diving here, would not be possible in a small group without a loss of our safety margin. And still we are all working until late at night.
Between the second and seventh day, teams of divers continued to film, survey and collect samples from the bottom of the Blue Hole. Objectives and strategies change with each viewing of the previous dive’s video footage. On June 7th, Ken Furman, Dr. Andrew Pitkin and Chris Johnson set out to the southwest wall of the Blue Hole to explore for speleothems and cave formations. A possible penetration point is found in the sheer underwater cliff at 245 ft, but time did not permit exploration. That duty, this time, would fall on the next day’s team – Matt and Terrence Tysall.
The Seventh Day (June 8, 1997)
The entrance to the underwater cave is at 245 feet – a little crack, almost invisible in the dark light at this depth under the overhang in which it lies. Just big enough to let a diver in back-mounted doubles and one stage bottle pass, the chimney goes straight up to a depth of 135 feet where it ends in a big chamber. The first look tells me and my partner Terrence that we hit the mother lode. This is not a coral cave, this is a solution cave. The chamber has a diameter of about 50 feet. Directly in front of me, in the absolute darkness illuminated only by our powerful cave lights, I see a giant turtle skull. Excited, I give Terrence a light signal to show him my find, and he shows me a complete six foot long turtle skeleton laying belly up on the edge of that chamber. In the progress of the exploration of this cave system, we find five complete turtle skeletons.
The water in the cave is so clear that it is hard to see it. Fine light brown silt is covering the floor, which looks like it is covered in flowstone. Visibility here can change dramatically if a diver does not move with the utmost care to prevent the silt from being stirred up – using the techniques of cave diving.
Slowly, we progress through the cave. My partner is laying the guideline in front of me. Floor to ceiling height in places is only enough to get through without back-mounted tanks. Visibility deteriorates fast. Our light beams light the little passages which haven’t seen light for thousands of years. In the corners there are lots of speleothems. In some parts of this cave it is highly decorated – the geologists are going to be happy. Jackpot. The floor is littered with hundreds of crab shells, covered with the light brown silt – entombed in the cave, like the turtles who couldn’t find the way out of this maze in absolute darkness. Throughout the cave we see dozens of small red shrimp and even some lobsters in the entrance area. On what they feed, I don’t know – maybe on fellow marine life who lost its way into this cave system.
The only sound is our bubbles which are collecting on the cave ceiling, which slowly work their way up to the surface through the porous rock layers, where they are seen by out fellow team members on the boat.
The cave passage is about 250 feet long, floor-to-ceiling height is between 2 feet and 6 feet. We reach our turn-around pressure and I have to leave this beautiful place after 45 minutes bottom time, but not without surveying the now permanent guideline and cave features in order to produce a basic grade 3 map the same evening.
After the extensive decompression, we surface with big smiles on our faces and agree to come back here tomorrow to film this beautiful cave for the planned documentation.
As Dr. Robert Dill and Dr. Tony Jones hear what we found and that we’ve seen lots of speleothems, they get really excited and outline the plan for tomorrow’s day of diving which will include shooting documentary video about the cave and the dive, including the surrounding area and the sampling of a stalactite and a stalagmite.
In the next four days the team completes many of the objectives set before them. The cave is revisited and documented, the west wall is searched for other possible cave systems and the large stalactite grotto is surveyed using depth / azimuth / distance techniques.
Preliminary dives are done in the cave just off Lighthouse Reef Resort with video and sample collections in preparation of the dive planned for the next day. Also, two core samples are retrieved from the center of the Blue hole (maximum depth 408 ft). The final mixed gas dive was planned for June 12.
The Eleventh And Last Diving Day (June 12, 1997)
The last mixed gas dive of this expedition will be conducted in the Abyss cave on the northwest of the Lighthouse Reef atoll where the geologists want to know how deep the Abyss is and if we can locate deep speleothems. The Abyss is much more protected than the Blue Hole due to the fact that the lid is still in place – the ceiling has not collapsed yet.
In the diving team are Ken Furman, Terrence Tysall, Dr. Andrew Pitkin and me, the German. Bottom mix is a 10/60 trimix. Tables were cut with the Adept deco software to a depth of 400, 430, 460 and 500 feet, just in case the Abyss goes that deep. 500 feet will be our MOD for the gas we are carrying. The run time will be 14 minutes (4 minutes to 220 feet where we do the switch from air to bottom mix and 10 minutes to and at maximum depth).
With us in the water are two support divers, Tim Gallagher and Steve Newman. On board the Aqua Venture are our second physician Dr. Clyde Martin, Dr. Robert Dill the chief geologist and Captain Frank Bounting. With them on the boat are 10 spare stage bottles with air, EAN40 and 100% O2. All of these will be in the water, staged at different depths in case one of us develops a gas management problem.
The descent begins along a permanent line from the mooring line to the entrance of the Abyss. In the entrance chimney we encounter bad visibility – most likely sediments stirred on previous dives. Along the permanent guideline we drop to a depth of 220 feet where we switch from travel gas (air) to bottom mix (10/60). The switch is done just below the H2S layer, you can clearly taste the sulfur there. Terrence is operating the video camera, Ken is producing enough light to make a blind man see, Andrew and I are leading and I am running the reel that we pick up at 310 feet (where Andrew tied it off a couple of days ago).
Just as I pick up the reel, I see a speleothem at a depth of 300 feet, but have no time to collect it – it is the deepest speleothem we have located so far. At about 320 feet it is getting really cold, we drop through a thermocline and are now in about 60-65 degree water.
It’s a smooth and slow, controlled descent. When my depth gauges show that we pass the 400 feet level and there is still no bottom to see it is dawning on me that this is going to be the deepest cave dive I have done so far. The first depth gauge freezes at 422 feet, leaving me two that work just fine. There the bottom comes into view. At 450 feet we hit the debris cone, made out of sand falling in through the chimney and building up a dune down here. On top of the dune is a metal fishing trap, useless at this depth where I don’t see any marine life at all. After I tied into the trap (no other stable objects are close) I look around to check on my dive partners. All there, everybody looking happy, lots of gas and lots of line on the reel, so I decide to swim slowly down the slope. We produce enough light to light up the place, in the distance we see the walls of this giant sinkhole, the video camera still recording the quiet, cold and dark place.
The silt is becoming much finer, still the color of sand with ripples in it, just like on the beach. At 14 minutes runtime, and at a depth of 485 feet, I come to my turnaround pressure. A little rock lies just in front of me. It must have fallen from the ceiling some time ago and gives me an ideal tie-off point. The bottom is still sloping down a little, but we can see the end of the Abyss, must be at about 500 feet maximum depth.
After the dive had been called, our slow, long ascent begins. I am not really comprehending that I an 485 feet deep in a cave. Our first safety stop is at 400 feet for one minute, the next one is at 300 feet for another minute. By then it looks like we are in a snowstorm, lots of white sediments falling on us, dropping the visibility to almost zero at 300ft. Once more, the guideline is the only lead out. At 220 feet, we switch back to our travel gas (air) and start our first deco stop at 200 feet. Once out of the chimney and the H2S layer, it becomes warm again. Clear water, full of light and our support divers are a very positive sight. We smile at each other and continue the major part of this dive – a more than three and a half hour decompression is still in front of us that will take a lot of concentration.
After almost four hours, we ascend with big smiles. Only one in our team has been deeper. Just out of our wetsuits, Dr. Pitkin is conducting Doppler tests and is very satisfied with the results – only low grade inert gas bubbles are detected, and only after knee bends.
A truly nice dive as a last dive for this successful expedition.
All in all, the team accomplished their objectives, and in most cases, exceeded them. In the two weeks teams: collected rock and core samples in the Blue Hole at depths of 320, 375 and 408 fsw, retrieved speleothem samples from 130 and 235 fsw, surveyed and mapped the only cave found on the southwest wall, surveyed and mapped thirty-three stalactites or columns covering approximately 400 feet of the south wall, established the maximum depth of the Abyss at 500 fsw, conducted Doppler tests after all mixed gas dives and recorded them on DAT for later analysis, completed tests for bacterial growth in oxygen rich regulators and conducted operations consisting of more than 20 dives on mixed gas between 320 and 485 fsw along with the corresponding deep air dives for support and reconnaissance.
The next two days were spent packing up and leaving the hospitality of the island resort and saying goodbye to the many friends that we made. The team members returned to their respective locations. The core samples went to Dr. Eugene Shinn in Saint Petersburg, Florida where they will be analyzed for Saharan Desert iron sediments. The other samples have made their way to the Radioactive Isotope Laroratory in New Mexico where Dr. Yemane Asmerom will begin his analysis of them.