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By Charles Roberson, Karst Underwater Research
Header photo by Kirill Egorov
Note: depths are shown in meters of freshwater (mfw) and feet of freshwater (ffw).
Karst Underwater Research (KUR) has a long history of exploration in Weeki Wachee cave system. Dives are conducted under a research permit from the Florida Park Service but the dive season is governed by the rise and fall of the local water table. The main spring entrance is only accessible during severe drought periods, but ever since Twin Dees (aka Little Spring) was connected in 2014, we have had safer and more reliable access to the system. Unfortunately, it’s not accessible at all times. When the groundwater rises beyond certain levels, the entrance shaft at Twin Dees becomes dangerous due to the high flow. Conversely, when the groundwater drops below certain levels, Twin Dees ceases to flow enough water to provide adequate visibility. It’s during the in-between periods of neither drought nor flood that Twin Dees allows divers to safely access the Weeki Wachee cave system.
Last dive season ended in the spring of 2019 with a significant new discovery. Karst Underwater Research (KUR) President Brett Hemphill had spotted a lead on the southeast wall of the White Stripe room during a video dive. Unable to dive for the next month due to work commitments in Palau, Brett gave fellow KUR directors Andy Pitkin and Matt Vinzant his blessing to explore this newfound lead. What Andy and Matt found was a whole new section of cave with significant flow. Not only did this section have flow, but it was also some of the deepest in the system with most passages below 110 mfw/ 360 ffw. Could this be the elusive water source for the entire system? In keeping with the Tolkien theme, they named the section Minas Tirith after the city of Gondor.
The team had to wait until the rains raised the groundwater levels and increased the flow in the small Twin Dees entrance. Conditions started to look promising during the summer, and the team undertook several setup dives to prepare for renewed dive operations. However, the summer rains raised the water levels faster than expected, and the window quickly shut due to high flow.
It wasn’t until December that the team was able to renew dive operations. On December 7th, Andy and Matt returned to the Minas Tirith section and pushed the end of their previous line. They continued approximately 168 m/550 ft into a large funnel-shaped breakdown room. Unable to find an obvious going passage, they fell back to a lead that Matt had spotted on their previous dive. This lead was located about two-thirds of the way into the Minas Tirith section on the southeast wall of a massive room that Pitkin’s son Miles named the Sirius room. The lead at the base of the room was at 113 m/370 ft and quickly led to another discovery that Matt dubbed the Unknown. The Unknown was actually two rooms conjoined in the middle. The first room was nearly vertical breakdown with a large window at the top opening to a shallower second room. Both rooms were large enough that it was nearly impossible to see both walls despite the clear, blue water. The team continued along the right wall of the second room into a small alcove they called the Attic, adding a total of 229 m/ 750 ft into the Unknown.
While the exploration team was underway, Brett Hemphill installed a new habitat in the fissure at 21m /70 ft. This habitat is suspended by bolted anchors and has two seats for divers. As our dives grow longer, this habitat will get us out of the water sooner, allowing us to do our 21-15 m/70-50 ft stops warm and relatively dry. The plan will be to run a habitat scrubber in this habitat the same as we currently do in the 12 m/ 40 ft habitat.
On December 14, Bob Beckner, Derek Ferguson, and Gary Donohue explored and surveyed 255 m /835 ft of passage that they named the Battle Plain. This large passage connects several of the short-cut passages together and has an average depth of 100 m / 330 ft.
Into The Unknown
A week later, Brett and I set off to explore the Unknown. On the way, we plugged in a battery pack and turned on the radio location ring that Andy and Matt had dropped at the top of the breakdown in the Sirius room. With the red LED indicating that the ring was transmitting, we headed down into the passage leading to the Unknown. Almost immediately we came to the bottom of a large breakdown with what appeared to be a lead to the right. Brett went partially into this lead and came back to tie in. As he was doing that, I went further in the lead since I was going to bird-dog out in front.
Unfortunately, as I went further in the passage, it became apparent that it ended in a room with an unique bowl-shaped floor. I quickly headed back and signaled Brett before he tied in his reel. We decided to head up into the Unknown and quickly followed Andy and Matt’s line into a small alcove with even smaller going passage, and we decided as they did that there were other more promising leads to be explored first. When you’re exploring a deep cave with multiple leads, you have to triage and go with the most obvious first, giving preference to the direction you think the cave is heading. This doesn’t always work out, and I’m sure we’ve overlooked some important passages.
As we came out of the alcove, I scootered across the huge room to see that there was a deeper-looking passage on the other side. I signaled Brett to tie in, and as he did I dropped down to make sure this wasn’t an alcove at the bottom edge of the breakdown. At first I wasn’t so sure, but as I descended below the duck-under I saw a cobalt blue passage with a white floor and walls reminiscent of the Post Mortem passage. These slightly smaller, deep passages seem to be the connective tissue between the huge rooms and shallower trunk passages in this system. As Brett came down the breakdown with the reel, the most obvious passage was to the right, which would hopefully go around the north side of the breakdown room and head east, which is the upstream gradient in this area. I went a few hundred feet and ended in what appeared to be a terminal room. As I scootered around the small room, I noticed a doorway on the right heading east. Just as I was getting my hopes up, I came into another perfectly round room, this time with no other exit. Brett tied off on the far side of the room and started surveying out. We had explored 179 m/ 587 ft of passage that we appropriately named Lost Hope.
On the way out, we checked the radio location ring at the top of the Sirius room. Sure enough, the LED had turned green, indicating that the surface team had successfully performed our deepest radio location to date at 104 m/ 340 ft. As such, we carried the ring back to the Mega-Y, where we dropped it for a second locate.
The Deepest Cave in Florida
The first weekend in February was our next opportunity for exploration. In the meantime, Kirill Egorov had captured some amazing photographs of Mount Doom and retrieved the radio locate ring. Andy and I made plans to check several known leads on the south side of the passage between the White Stripe and Sirius rooms. Andy was to check the leads while I kept an eye on the guideline, and if it went, he would bird-dog out front while I ran the reel. Andy checked what initially appeared to be a large alcove just before the Sirius room but found an ongoing passage on the left side and gave me the signal.
As I tied in the reel and followed him through the archway, it opened up and turned to the south, which was exactly where we wanted to go. This entire section of the cave is below 107 m/350 ft, and as I looked at my gauge, I realized we were exploring at 122 m/ 400 ft. Andy scouted ahead as the passage came up into a large breakdown room. The way ahead wasn’t apparent until we crested the breakdown and saw the going passage on the other side. After 207 m/680 ft of new passage, we came slightly up into the familiar looking White Stripe room. We immediately saw the line and tied into an existing tie-off at about 113 m/370 ft.
Now it was my turn to look around as Andy surveyed the new line. On the way back, I spotted a possible lead on the south side of the breakdown room and dropped down to check it out. In doing so, I not only found a likely going passage but hit 126 m/ 414 ft, setting a new depth record for Florida caves
On the way back, I spotted a possible lead on the south side of the breakdown room and dropped down to check it out. In doing so, I not only found a likely going passage but hit 126 m/ 414 ft, setting a new depth record for Florida caves.
Closer to where we started exploring, I also spotted another likely passage headed southeast. Normally a big loop would be disappointing, but this loop may open up one or more leads in the southeasterly direction, which is the upland gradient in this area.
A dry winter without much rain meant that the groundwater levels were dropping quickly. With only a few more weekends of diving available due to conditions and the threat of the COVID-19 pandemic shutting down the state parks, we made plans for two final exploration dives of the season. In mid-March, Brett and Andy checked the deep leads in the loop passage we had discovered on the previous dive. All the leads they checked turned out to be small without significant flow.
Racing the Pandemic
The next weekend, Matt and I headed in to check several leads, and the team rallied to pull nine safeties from the cave. Our first stop was a lead I had spotted at the start of the large loop that Andy Pitkin and I had put in several weeks prior. I initially looked into this lead while Andy was surveying and expected to see the large breakdown of the Sirius room, but to my surprise that’s not what I saw. I still thought this may just be a short loop, so I asked Matt to go to the base of the breakdown in the Sirius room, and I would quickly go in and look for his light.
As I went in through the window, I realized immediately that it was a medium-sized room with a passage headed off to the right or southeast. I looked around the room and didn’t see Matt’s light right away, but as I headed over to the left side, I saw the faint glow of his light beyond a duck-under in the Sirius room. I headed over closer and realized it was too small to pass, so I headed out. Matt obviously had the same idea, and we met in the middle. I gave him the signal that it went and signaled him to tie in to the existing line.
I bird-dogged as Matt followed with the reel, and we quickly entered the passage to the southeast of the room. I caught a quick glance at my depth as we descended past 128 m/420 ft. We dropped into what appeared to be a terminal room with conglomerates of rusty sand dollars on the ceiling. There were two low restrictions at 131 m/429 ft that opened up after a few feet, but there were no signs of flow, so Matt tied off as I started to survey out.
Our next stop was the Unknown. At the base of the Unknown is a room on the right that curves around and looks like it may go. I held on to the line while Matt checked this room again but as before, he found that it didn’t go. Matt and Andy had ended their exploration of the Unknown in the far east corner of the second room, the Attic. We checked that again without success. We also dropped down into the False Hope passage that Brett and I had explored on a previous dive. Unfortunately, the leads we had seen were low and had no signs of flow. Matt did spot one narrow lead with a bit of flow that could possibly skirt the northwest side of the breakdown.
Luckily, we had one more lead to check that I had spotted on the way in at the bottom of Mount Doom. Until recently, Mount Doom was the deepest part of the cave at 124 m/407 ft. The lead was on the far side of a saddle, which made it hard to see unless you were on the far south wall looking straight down. As I came through the restriction up into Mount Doom, I went left over the saddle rather than right toward the exit. I paused long enough to flash Matt, and he quickly headed back my way as I dropped straight down in the crease toward the white sand ripples at the bottom. The duck-under was large enough to pass, and I could see a room on the other side. I went through knowing that the glow of Matt’s light would provide a reference to exit. The room was wide and had at least one going passage to the south. We had no time to explore it further, so it will have to wait until next season.
As I write this season recap at the beginning of summer, the groundwater levels are still dropping due to the unseasonably dry winter. Hopefully, the summer rains will recharge the system quickly so we can get back in and explore the newly discovered passage at the bottom of Mount Doom. Until then, KUR divers will continue to focus on other projects.
Charlie Roberson is an attorney who lives and works in Gainesville, Florida. He is the founder of FATHOM Dive Systems, LLC, a manufacturing company that focuses on life-support equipment for underwater exploration.
Charlie learned to dive in 1991 while serving in the U.S. Navy. He then spent the next two years diving the wrecks and deep walls of the Western Pacific. After returning to the states, he moved to Gainesville to attend the University of Florida and take up cave diving. Years later, he is still cave diving and currently holds the world record for penetration in an underwater cave at 8,208 m/26,930 ft.
Charlie is a director of Karst Underwater Research (KUR) and has participated in numerous KUR exploration and survey projects. Most recently, he traveled to Mexico for expedition caving projects in the Peña Colorada and Río Uluapan. Charlie also serves as the preserve manager for the National Speleological Society’s Mill Creek Sink Preserve and as the diving coordinator for Florida Speleological Researchers’ Diepolder cave system.
They Discovered an 11,000-year-old Submerged Ochre Mine
The exploration crew at CINDAQ, headquartered at Zero Gravity Dive Center in Puerto Aventuras made international news this year with their discovery of an ancient submerged ochre mine. Fortunately, they were happy to share the secrets of its discovery and how they documented their find with British cave and 3D photogrammetry instructor John Kendall. Oculus Rifts anyone?
By John Kendall
Header image courtesy of CINDAQ
In 2017, underwater cave explorers Fred Devos, Christophe Le Maillot, and Sam Meacham found evidence of ancient mining activity while exploring and mapping new tunnels of an underwater cave near Akumal, Quintana Roo, Mexico. Historians know that ancient residents actively mined pigment and other minerals from the caves of the Yucatan Peninsula, but the ancient mines the CINDAQ team discovered are now submerged, indicating that such mineral exploitation occurred thousands of years ago.
At the end of the last Ice Age, intrepid miners ventured deep into these tunnels with torches in hand. The navigational markers, mining debris, fire pits, and excavation pits they left behind are now entirely underwater. Over the last three years, the three explorers (along with others) have been surveying the site and making 3D photogrammetric models of the mine workings. As the mine has been submerged for around 8,000 years, it’s been untouched since then, and it’s an amazing time capsule. The project recently hit the international news when the first results were published. I was pleased to be able to chat with Chris, Fred, and Sam to find out a bit more about the project, and the challenges faced with archaeological work in a cave environment.
John Kendall: How did you happen to find the mine?
Chris Le Maillot: As always, there was a little bit of chance involved with it. The cave—Sagitario, which is a beautiful cave behind Minotauro—was initially explored by a few local cave divers. They established an upstream and part of a downstream, dropping down in the upstream to around 22 m/72 ft, and there’s the halocline sitting at that depth. It’s not always the case, but they didn’t take any survey, absolutely nothing. So I don’t think the information was there for them to continue on with the exploration. As you know, once you have that data in and have a good concept of what the cave is doing and where it’s going, it’s easier for you to poke around and find potential continuations of the cave passages.
So one of the divers asked Fred [Devos] to get involved to create a survey. That comes from the fact that Fred previously had done some mapping for these guys. Fred had a cave survey class coming up, so he took the class there, and spent the week with the survey class mapping the downstream part. Obviously, when they got to the end of the line, Fred could see that there was potential for further exploration. But you can’t really go off exploring during a class, so he went back with Sam [Meacham].
So then you went back and explored?
Fred Devos: Exploring caves is what we’ve been doing for more than 20 years, and so it’s a regular event during the mapping of a cave to find more cave to explore. You know, when mapping, we have to swim off to measure the side walls, sometimes there isn’t a wall, and then end up exploring that passage. I was in the process of making a detailed map of this cave, and found this passage, so I went back with Sam, and we immediately realized something was unusual. Things were out of place, we started seeing rocks piled on top of each other, speleothems in places they shouldn’t have been, and the further we went the more of this we saw.
“Exploring caves is what we’ve been doing for more than 20 years, and so it’s a regular event during the mapping of a cave to find more cave to explore.”
We started picking up a little bit of flow, which is always a good thing in exploration, and that led us to this restriction, where all the water was going through, and I don’t think we’d have made it through if the restriction hadn’t been manipulated before we got there. So, you know, speleothems were smashed out, and it really looked like 100 divers had gone through there before us, which really piqued our curiosity as we knew no one had been there before us. We happened to be in back mount during this dive and I managed to squeeze through there and called Sam through, and that was when we first saw irrefutable evidence of what humans had been doing in this cave—you know, pre-8,000 years ago.
“It was pretty clear to anyone what we were seeing, that people had been digging in here, smashing open the floor and pulling out huge amounts of sediment and piling stuff out of the way. It was super exciting.”
We didn’t have to wait for lab results to come back or ask an archaeologist about it. It was pretty clear to anyone what we were seeing, that people had been digging in here, smashing open the floor and pulling out huge amounts of sediment and piling stuff out of the way. It was super exciting, as it was something we’d suspected for quite a while but had never really determined for sure that was what we were seeing. But this time it was obvious, and there was no question about it.
So, how large an area does the mine occupy?
Sam Meacham: It’s about 250 m/817 ft of cave passageways that are exemplary of the mining activity, and everything we’re seeing there shows the things that people were doing in the mine.
Devos: And we haven’t finished exploring yet. There are hectares of mining area, so it’s not just one hole that’s been dug out. It’s entire passages and we’re talking about hundreds, maybe thousands of tons of material, and remember we have dates spanning maybe a 2,000-year period.
What makes La Mina so significant from a scientific point of view?
Devos: The amount of workings means that this was a massive undertaking. Not just the mining itself, but it’s clear it wasn’t just a one-person adventure. It must have been multi-generational, but beyond that it speaks very much about the organization of the people of that time. So as you can imagine, they were in a dark cave and needed fire for light. So they needed people to bring in the firewood, and others to cart out the material, and there were probably explorers at the time. You know, people that ventured further into the caves away from the exit into the smaller passages…to find this very valuable resource. And I imagine they were the ones that were being punished somehow because the risk involved was probably much greater. So, you know, if they didn’t do their work well in the mine, they probably got sent to explore.
So are there any archaeological signs on the surface around the mine?
Devos: Well there probably are, there’s certainly Maya era archaeology, and in almost every cave we see evidence of that, but we’re talking about 5,000 years ago. The mine was even further back, so anything that was once there won’t be anymore, and the only place we are likely to find anything is in the caves.
Let’s chat about the photogrammetry side. More and more people are hearing about photogrammetry, but I think the readers will be interested to hear a bit more about the challenges that you faced doing photogrammetry in a cave environment, where everything around you is archaeological.
Meacham: I think that can get us started on an interesting concept. In 2010, Chris, Fred, and I, Beto Nava, as well and Franco Attolini and Danny Riordan and Roberto Chavez, all did our underwater archeology course here in Mexico with the Nautical Archeology Society that was supported by the National Institute of Anthropology and History (INAH). It empowered us.
And by having that NAS certification, it kind of helped check a box for the Institute. And, you know, they could say if anybody questioned our abilities, well, we’ve got the certification.
I’d say the genesis of this for all of us here was the Hoyo Negro project, and with the exploration followed by the high grade survey, and then the photogrammetry, which is another whole level in itself. The major problem in Negro is the pit itself—it’s just immense—and how do you document something like that? So we worked with Beto and the team who came up with a grid system at 34 m/110 ft depth, and then it’s every 0.8 m/2.5 ft with a cookie on the line, and so it’s a systematic grid. The difficulty there is that it’s not just a nice flat bottom, it goes from 40 m/130 ft to about 55 m/179 ft, and it just becomes really complex.
But basically what I’ve been doing there is assisting with the lighting or helping Beto. So when we jump forward to doing the mine, it’s a completely different environment. There’s no pit—it’s a continuous cave—so there was no way we could put in a grid, and I’ve never really done photogrammetry before. I had observed it being done, but I was starting from scratch in terms of my own experience. So it was a challenge, but I had plenty of people to go to as resources, and who could check out what I’d done and help make it better. And what’s interesting about the big model is that you can see my progression as we go around, and now of course I want to go back and do it all over again.
So in terms of the challenges, I bought a Sony A7S camera and a Nauticam housing for it, and we just went in and started taking a bunch of photographs, came back, and put it into Agisoft. I have to say my expectations were low, but we were all pleasantly surprised when the model came back. This is like, “Wow that’s what we’re actually seeing there,” and it’s so cool. So that gave me the confidence to say, “I think I can do this,” and we basically picked about 250 m/817 ft of cave passage, which is a great example of the mining activity and of seeing what people were doing there.
That sounds like quite a learning curve, and a big challenge.
Meacham: Yes, we just started going in and piece by piece doing sections of the cave. I can’t remember how long in total we were down there. I’m sure it’s written down somewhere, but we took something around 18,000 photos. And as you know, taking the photos is probably the easiest part. Having the computing power and post-processing of the images is the key. A lot of people treat Agisoft as a bit of a black box, but you know it’s garbage in, garbage out. So in terms of the environment, we’re talking about a ceiling height that’s minimal, and while you can fit through OK, you want to be as high as possible for the photogrammetry in order to cover more area.
“I’m sure it’s written down somewhere, but we took something around 18,000 photos. And as you know, taking the photos is probably the easiest part. Having the computing power and post-processing of the images is the key.”
So, we just worked section by section, using the line as a reference. I was going down the line and started by making sure that I got any markers on it, and then going back and forth to get all the photos. The person that suffered the most was whoever was assigned to dive with me, as they just had to sit there and watch me go back and forth while taking the photos.
18,000 images! That’s a whole lot of processing.
Sam Meacham: Yes, we’re lucky to have the guys at University of California at San Diego (UCSD) helping us with the processing. I probably started off taking too many photos, but the computer guys complimented us on the photos and the overlap and coverage.
So what about other survey techniques, was there anything special about mapping this site?
Devos: We surveyed the first part of the cave, and that was pretty normal, but once we found the mine, then suddenly we had a need for all these new types of symbols that didn’t exist before for cave survey. I tried to think about what would be interesting to make notes of, but I didn’t want to speculate as to whether something was a natural pit or whether it was digging.
So we came up with three new symbols. There was already a symbol for a pit, but we added a jagged line on the pit to show that there was a broken edge, so it was smashed. Then we came up with a symbol for a displaced object, so if you see some stalactites and there was no way it came from the ceiling above, then that’s a displaced object. And then if you have stacked objects, so objects placed on top of each other, we had a symbol for that. We then made all of these colored red. I chose red because of the extracted material, the ochre. Also, when you look at the map, and you see all that red, it really shows the extent of the manipulation of the cave. It really brings it out, and I think that’s the most important thing about this cave. Sidewall information is nice, but this is very much an archaeological site.
So what’s next with the site? Any further diving plans?
Devos: We have some plans in place. The map that we’ve made, the photogrammetry, and the video documentation, even the exploration are not finished. So we actually concentrated on one area and tried to get that in the bag, you know, and focus our studies and our samples in that area, without stretching too far, but there’s still a huge portion to go. The technology really helps here, because you can bring that information out for the scientists and others to see. And then there’s much less need for others to go back there.
And this is really the part where we don’t know what’s going to happen. Are divers one day going to be able to go there to tour this site? Luckily, I’m not the one who will be making that decision; there is an archaeological department in Mexico who set the rules. But these conversations are starting, and we’re not really sure where they will lead. But for now we are doing what we can to secure the documentation of the site and working closely with the archaeologists and the landowner.
So a last question: What would your advice be to a diver who is just starting out on their GUE journey, and who hears about this and other projects, and wants to one day join?
Devos: We have been running all kinds of projects down here for years: exploration, science, surveys. Come and get involved, and help out. Good basic training helps open up the door.
Meacham: Once you’ve trained and gained enough experience to become confident in whatever environment you’re interested in, then come and get involved. There’s great training with the GUE Documentation Diver program, Science Diver, Photogrammetry Diver, and Cave Survey where you can actually put these skills to the test. Everyone on a project is an important part of making it work. Obviously it becomes tricky when archaeology is involved, as there can be federal laws and regulations that restrict access, and so we can’t always put just anyone onto a site, but there are all sorts of projects within GUE to help develop those skills and get known by project leaders.
Le Maillot: Of course, project diving is what GUE has been known for since the very beginning. So I think making that initial step to take training with GUE is an important one in the right direction. That’s the starting point of understanding how we are organized, the procedures that we use, [and] the team aspects of all our diving. And then it’s about thinking about what you want to do.
“Of course, project diving is what GUE has been known for since the very beginning. So I think making that initial step to take training with GUE is an important one in the right direction.”
If you’re interested in wrecks, you have Mario Arena in Sicily or Richard Lundgren with the Mars project, and you’re naturally going to be headed down the Tech 1/CCR route. If it’s the stuff in Florida, or Bosnia, or here in Mexico, and the cave thing really rocks your boat, then that’s where the GUE cave training comes in. Then, as you progress with your tech or cave training, you will get to know divers who are involved in projects, and that could be your instructor. You know, if you come here to do some cave diving in Mexico, then Fred is going to mention a few things about survey and cave projects in Mexico and around the world. So that will start opening up a different perspective for you.
Watch a Video of the Mine on GUE.tv. (Requires a GUE.tv membership or signing up for a free trial)
For more information about the La Mina project, you can visit the CINDAQ website
Check out the CINDAQ YouTube channel
John Kendall is a GUE technical, cave, and CCR instructor living in the UK. Since he was a small child, John has been fascinated by the underwater environment and the possibilities of adventure, and he is grateful to GUE for helping him to turn those childhood dreams into reality. As an instructor, John regularly travels around the world teaching GUE classes and helping to build local GUE communities. For the last 5 years, John has been working with underwater 3D Photogrammetry as a technique for nautical archaeology. This cutting edge technique allows for digital 3D models to be created of shipwrecks and caves, and allows researchers and scientists unparalleled abilities to manipulate and navigate the sites from the comfort of their own computers. John was the primary author of the GUE Photogrammetry class. He is also a member of the GUE Training Council and a Fellow of the Explorers Club.
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