Boesmansgat.. or Bushman’s Hole..

This hole is believed to be the third-deepest submerged freshwater cave (or sinkhole) in the world, approximately 270 meters (886 feet) deep. It is located in the Northern Cape province of South Africa.

Boesmansgat was believed to be first explored by amateur diver Mike Rathbourne in 1977.

On November 24, 2004, Verna van Schaik set the existing Guinness Woman’s World Record for the deepest dive with a dive to 221 meters (725ft). What some people won’t do for fun.

Of course as per all dangerous sports, the sport of cave diving has it’s toll and here is the roll of honour..

Eben Leyden died in 1993 after blacking out at 200 feet.

In 1994, while helping a team prepare for a dive, Deon Dreyer died.

On January 8, 2005, famed deep cave diver Dave Shaw died while recovering Dreyer’s remains from a depth of over 800 feet (about 245 meters). Shaw, using a re-breather apparatus and suffering from nitrogen narcosis while attempting to place the remains in a body bag, became entangled in his own lines and blacked out. Later, as the recovery team was removing equipment, both bodies floated to the surface, apparently pulled to a depth where the gasses in Shaw’s body expanded and gave it buoyancy.

HomepageSlideshow_RaisingtheDead_021212courtesy of Outside Magazine with their article of “Raising the Dead” click to read the article.

Facts I found while researching these deaths, it takes them only 15 odd minutes to get down to these vast depths, but apparently up to 13 hours to ascend, due to the fear of the bends. Madness if you ask me..

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But how did this hole in the middle of the Kalahari develop? Who knows, was it an air bubble that came to the surface when the area was volcanically forming? Was it a lime stone deposit or pipe that has eroded with time? An area of cracking in the surface?

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The hole is located on a farm, no sign posts to it, or advertising, but word of mouth has you exploring and asking the farmers permission to go to it. A slight rise in an otherwise flat terrain brings you to the site.. a deep hole, approx. 20 metres down and a precarious descent, one can spy the water surface, a green slush. But all divers reports are of a beautiful crystal clear water below the surface.

The rock formations are fascinating and here are but a few of those I took..

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97 thoughts on “Boesmansgat.. or Bushman’s Hole..

  1. Hi Bulldog,

    I first heard about the Bushman’s Hole when my daughter (who is a SCUBA diver) loaned me her copy of the full book “Raising The Dead”.

    Please note that I am also a SCUBA diver, but not a technical diver, although this book taught me a huge amount about technical diving, and I have discussed all I learned with a friend who is a qualified technical diver.

    Based on what is in the book, you have two errors in your write-up about the death of Dave Shaw, and another in the story of death of Deon Dreyer.

    Note: This is not criticism of your write-up, just an attempt to ensure that the story (as I have read in the book) is also stated here.

    A quick glossary for non-divers:
    – Air: Generally, what we breathe – about 20% oxygen, 78% nitrogen, 1% argon and 1% other gases
    – Air mix: A mixture of gases that includes oxygen, but may contain significantly different percentages of gases as compared to normal air.
    – Nitrox: A mixture of oxygen and nitrogen that has different percentages to conventional air.
    – Rebreather: A machine that keeps the majority of air exhaled, removes (“scrubs”) the carbon dioxide, and replaces the oxygen. This allows very long dives without having to carry a huge amount of air mix.
    – Buddy: A partner in a dive; each must keep in contact with the other throughout the dive.
    – Nitrogen narcosis: A giddy, drunk feeling that occurs when the amount of nitrogen dissolved in the blood stream exceeds a certain amount. Can be very disorienting, and some people do extremely stupid things when affected (like taking their air-regulator out of their mouth).
    – Partial pressure: The pressure of a specific gas in a gas mixture at the current pressure. At the surface, the pressure is 1 atmosphere, and oxygen is roughly 20%, so its partial pressure is 0.2.
    – Depth pressure: The pressure that you experience on your body at a specific depth. Each 10 metres of depth increases the pressure on your body by one atmosphere. Therefore, at the surface, your depth pressure is one atmosphere. 20 metres under water, your depth pressure is 3 atmospheres.

    With respect to the death of Deon Dreyer, he was in a group of divers who all had buddies, and were holding at a depth of roughly 50 metres on a descent line. They were all feeling some effects of nitrogen narcosis, as they were breathing Nitrox. The lead diver realised that Deon wasn’t with his buddy (who was his brother), and indicated to him, questioning “Where is your brother?” When Deon’s brother shrugged in response, the lead diver looked down, and could see a head-lamp descending further down the line. He tried to power down after him, but rapidly concluded that the light was falling away faster than he was descending, so he aborted. Later, he realised that he had not seen any bubbles rising, implying that Deon had rapidly dropped into a deeply unconscious state, and ceased breathing. At shallow depths, this is referred to a shallow water blackout. At 50 metres, it is questionable that this is the applicable term.

    With respect to the death of Dave Shaw, I need to explain what depth does to gases we safely breathe at the surface.

    Given enough pressure, *every* gas is poisonous to human beings – even oxygen. Oxygen starts to become poisonous at 1.2 atmospheres partial pressure. Therefore, standard air (20% oxygen) at 6 atmospheres pressure (giving 1.2 atmospheres partial pressure of oxygen) is starting to become poisonous. Once the oxygen level exceeds 1.4 atmospheres partial pressure, you likely have only a few minutes to live, most of them unconscious.

    Therefore, at 270 metres depth, the pressure will be 28 atmospheres. This means that 4.2% oxygen would be poisonous, and 5.0% would be potentially deadly. Dave Shaw had been intending to maintain 4.0% oxygen at the bottom of the dive (the remainder of the gas in his rebreather being 80% helium and 16% nitrogen). Specifically, while he had nitrogen in his rebreather air mixture, there was nothing that implied he had suffered nitrogen narcosis.

    I also need to explain why a rebreather is a very dangerous device, and needs very accurate control.

    Our impulse to breathe is triggered by the presence of carbon dioxide in our lungs – when that rises about a particular level, we feel obliged to breathe. Without carbon dioxide in our lungs, we do not feel any need to breathe. Therefore, a rebreather is a very dangerous device – it “scrubs” the carbon dioxide from the exhaled air, allowing the remnant oxygen and air mix to be reused (called “the loop”). Sensors and a computer are used to ensure that the oxygen level in the recirculated air is maintained at a safe level, with the computer taking into account the depth at which the person is operating. However, as diving at the depths involved in this dive is on the extremely extreme side of extreme, no rebreather controller is certified to operate properly at these depths – the user must manually monitor the oxygen levels to ensure they are staying within sensible bounds.

    Dave and the team had taken significant advice about what was the likely state of the body of Deon Dreyer, and had been repeatedly informed that it would essentially be bones inside a wet suit. This was completely incorrect, leading to improper preparation and expectations. Simplistically (and not technically correct), the body was saponified (all body fat converted to soap), making the body significantly lighter than water. However, it was stuck in the mud on the bottom.

    By this time, it can be seen that there was a huge number of potential areas for disaster.

    However, the main contributing cause of Dave Shaw’s death was equipment failure – his rebreather monitor, (a wrist-worn computer that advised the rebreather’s oxygen level) had broken under the extreme pressure (there is a complicated story behind that), meaning that Dave was having to manually control his oxygen feed into his rebreather without accurate knowledge of the oxygen concentration within the loop. Based on the video his own helmet-mounted camera recorded, in the confusion of events that occurred when he freed the body and it started to float, his line became tangled and, concentrating on this, he lost concentration related to the rebreather control.

    Most likely, his oxygen level dropped too low and the lack of carbon dioxide in the gas he was breathing (almost pure helium / nitrogen) meant that he had no body warnings that he was running out of oxygen. He simply passed out and, entangled in the line attached to the body of Deon Dreyer, was dragged up.

    A more technically accurate description of Deon Dreyer’s body decomposition and of the exact events immediately prior to Dave Shaw’s death can be found on the Wikipedia page related to Dave Shaw.

    The Wikipedia article has a statement about the timing of the ascent of the bodies that contradicts the account in the “Raising The Dead”, implying that the other descriptions may also be inaccurate.

    Please note that my write-up here does not do justice to the full story, which gives huge background into the amazing person who was Dave Shaw. I strongly encourage anyone who has the least interest in knowing *why* anyone would think of doing something like this to read the book.

    • Hi Paul
      Thanks for this very interesting comment. Firstly I must ask you to note that I’m a amateur photographer and joy riding with my son in that area (he worked at Kathu) we in passing popped in to the farm… the owner very kindly allowed us to visit the site and naturally the camera begann to wiz. .. as an avid blogger at the time I had to share a bit of the story around the hole and did a little googling about it. What I wrote is what I found on the internet and hoped that it was fairly factual. I realise your comment is not criticism yet does enhance my write up and for that I thank you.. I never expected to get so many visits, comments etc on this blog as it is by no means a speciality of mine. Yet comments like yours adds to the blog, which by the way has had more than 10 000 reads, and I’ve noticed most readers from all over the world have read the comments.
      So your comment just makes my blog more stronger and for that I thank you.
      You can probably see of the 800 plus blogs I’ve written, most are of birds and animals which has gained me the world wide following that I have of my photography.
      Thanks again for your very detailed comment that will help others to gather more info on the hole in the middle of nowhere..
      Best regards.

      • Many thanks Bulldog,

        I had the great pleasure very recently (9th through 20th December 2018) to visit your beautiful country on business. I was mainly working in the Rustenburg through Boshoek area, so did not get any chance to visit “the hole”, although I definitely want to!

        I did get the chance to visit the Pilanesberg National Park and had a fantastic time there on a night safari drive (it started a little after 17:00, so it was more of an evening safari drive). I was able to get some fantastic (and rare) photos, including Black Rhinoceros, Leopard and African Hunting Dog. Sadly, we saw very few birds.

        I have promised my family (wife and two daughters, both in their 20s) that we will visit South Africa in 2020, and I hope to include the Bushman’s Hole in that visit.

        Thank you too for your positive response to what I wrote – I did have the advantage of having read a thoroughly researched book, so I wanted to be sure that what I wrote was not taken as criticism.

        w.r.t. the surprising response to the “left-field”, I have often found this to be the case. I too blog, but nowhere near as prolifically as yourself. A controversial, but reasonable, post of mine was reposted widely! It too was on a topic that was not “main-stream” for me.

        • Hi Paul
          It is always nice to hear visitors enjoyed my country… although I grew up in Rhodesia (will never associate with Zimbabwe) I do consider RSA my country… if you do return to us and visit the hole and want to see the best game park, make a visit to the Kalahari Gemsbok Park… it is the best in the RSA.. I unfortunately now live on the other side of the country in the Lydenburg district where I designed and built a golf course for a very rich man.. if I was still in the Northern Cape the Gemsbok park would be an annual visit for me.. there is actually so much to see that side of the country, research a bit, you might just find yourself spending more time in that area…
          Thanks again for your comment,
          Best regards

  2. Boesmansgat was formed as the rocks are soluble dolomite and so was dissolved by the ground water up to the point where it caved in when the weight of the top rocks became too heavy, .

  3. Amazing! I would never have the courage to dive into something like that! I love the pictures you took of the area though. It would be a fun and very interesting place to visit. So many beautiful creations on this earth of ours and I hope to see many of them at least in the USA like the Grand Canyon.

    • Now that I would love to see myself… my son saw it when he visited the USA, he says it is too difficult to describe what he saw… it is a lovely place to see in the middle of know where…

    • Thanks Jewels.. i was thinking of doing another about the cave and rescue of the bodies, but it has already been done and funny there is a link there to my blog…

  4. I googled it too….first page, as well. You did a great job with it, Bulldog!! People are crazy!! I always wonder how much they truly value their lives and those around them that love them to take such risks. It seems so very foolish to me. But, I am a party pooper, I guess.

  5. This is fascinating, and tragic. Excellent photos and research. Deep diving in a hole notorious for its fatal accidents is not my cup of tea. Most of my adventures occur in my own mind, and that seems to satisfy, but I feel terrible for those who lost their lives, especially the one who was just attempting a good deed, trying to recover the other diver’s body.

  6. Fascinating! My theory is that all this area was under water aeons ago. I have seen similar limestone deposits in Northern Ontario, Canada where we collected small fossils of ancient creatures in the limestone. This old Earth has seen some amazing changes. Thanks for sharing this. God bless those who go where others fear to tread!

    • This was on a trip between two golf courses… couldn’t resist the turning in after seeing the caves, and being told about this hole…lol

  7. You wouldn’t get me standing anywhere near the edge of that cliff, never mind diving off. I’ll forgo the adrenalin rush rather than risk a heart attack.

  8. Sinkholes are really fascinating. We came across many of them when we visited some of the archeological ruins on the Yucatan Peninsula in Mexico. I do not understand the need to explore them at the depths these divers do. Guess I am just not as adventurous as some (or crazy). Great photos and information Bulldog. 🙂

  9. I don’t think I’d be diving into that hole. I’d never heard of this before, Bulldog – thanks so much for posting the pics and the history. Very interesting! (I love learning about these unusual places for my stories) 😉

  10. Fascinating and great photos!
    That guy is standing way too close to the edge for me. I get those butterflies of fear in my stomach just looking at the photo

  11. WOW! I’ve always been fascinated by things like this…but the cave diving is terrifying to me! Here in Florida we have to worry about sinkholes…but nothing on the magnitude of something like this!

  12. I remember reading the fascinating and tragic account of the divers and what happened to the one that went in to recover the body of the earlier diver. So, this is where it happened. Wow. Thank you for this interesting post, bulldog.

    Russ

  13. This is fascinating. i agree with you, it is madness to go diving in caves. I was snorkeling recently and that’s thrilling. Diving beyond 20 meters in a cave is not my cup of tea.

  14. I am in awe! Thanks so much for circling the 6-foot man–it really does help give a sense of the enormity of this space. I was also fascinated with the fact that descending isn’t the problem, but the ascension taking so long! I had no idea the ratio was so uneven! Everything about this cave is dramatic and I’m so impressed. The more you share about South Africa the greater my understanding of it’s incredible richness. I suppose the quality of these natural phenomena inspire the adventure-seekers, but cave diving sounds insane to me! Exhilarating perhaps, but also crazy! 🙂

    • Thank you.. I think the attraction of being the first is what drives people to get to the bottom of the hole.. much like Everest there must be a bragging right that comes with it.. for me I want no such right..
      Our country has so much to offer, and probably as yet is still needing a lot of discovery, so many places to see and so many places to visit.. I feel I might just run out of time before I see all I want to here in my own country..

  15. Completely fascinating! There seem to be numerous caves on private land where the owners simply don’t want them known about. I came across a few in my cave exploration days, and was allowed to explore them on condition I kept a buttoned lip.

    • Glad you agree.. somehow my impression of you is not one who would go packing a huge engine on your back and diving into a deep hole… your intellectual level tells me that…

  16. Wow, fascinating history behind your amazing photography, Bulldog. Almost like being there my friend. I’d love to actually be there, now that I think on it. Thank you, a excellent share!

  17. It is madness to me as well. It’s amazing, though, how when someone has a passion for something, they will commit madness! I love the ‘exploratory’ nature us humans have.

  18. Oh goodness – this sounds very scary — your photos are amazing however. How on earth did you manage to capture them? Brilliant photograph Bulldog!
    With Love ~ RL

  19. Very interesting. I’m a certified scuba diver but I don’t think I would ever attempt to dive there. :-). When I was watching the series on Africa, in one episode they went into a very deep freshwater lake. I’m not sure if it’s the same one you’re describing. There were a lot of blind catfish in the lake.

    • I wouldn’t know if it was this one.. I didn’t know this existed till we came upon it… although through the news and papers I do remember reading of the deaths… I like to keep my head above water.. a good swimmer but snorkeling is good enough for me…

  20. I dive … but never in my foot or my goggles will I go down in that hole, not that brave – what a interesting place and great post. What would we do if we fell in ???? I would stay very fare of the edge … that for sure.
    Never heard about before – some people are just mad and wired = extreme sport, better on the golf course.or ????

  21. It would make more sense (and money) to send down one of those submersible bathyspheres to find out what it’s like on the bottom rather than risk one’s life. Amazing post, Rob.

    • Thank you Anneli.. I agree, but then one has to wonder why people climb Everest and do things of this nature.. do you think its an adrenaline rush or shear madness… I go with the madness…

    • Thank you… why anyone would want to do it I don’t know… but for such a hole to form in the middle of nowhere is what fascinates me…

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