This is a great question. There are all sorts of extreme technical challenges associated with spelunking. In many ways, spelunking deep caves is much more difficult than high peak mountaineering.
For one, the amount of equipment needed far exceeds that of mountaineering. A deep expedition will use specialized camping gear, food, lights, SCUBA re-breathers, suspension gear and literally miles of rope.
The spelunkers must go slowly as mistakes/injuries put the everyone in the expedition in danger. Think about how difficult it would be to have to haul a non-ambulatory person out from the bottom of a cave.
It’s dark and cold. Spelunkers do not use their lights unless absolutely necessary to save on power. This slows everything down.
It’s also very wet. These caves are filled with flowing water howling winds. Spelunkers are constantly soaked. The nature of caves ensures that no permanent base camps can be set up. The water will destroy anything you leave down there, so every time they go in, they essentially must start all over.
And I haven’t even touched on sumps yet. Caves are just basically massive water conduits. Every so often they form what they call sumps. They look like pools but really there are completely flooded sections of the cave, beneath the water’s surface. That’s why they need the re-breather equipment, because once you hit a sump, you have to swim through it. Navigating sumps is the most dangerous part of spelunking.
If you, or anyone else, truly are interested in this then I recommend checking out Blind Descent. It goes into great detail on just how truly difficult it is to explore these caves. It also details the rare breed of person that takes on the challenge of exploring the deep caves. One of the most fascinating books I have ever read.
Alright this all sounds great but these expeditions sound like the perfect opportunity for an elaborate and terrifying prank. I normally hate pranks but this is too perfect.
Spelunk down ahead of an expedition of your friends with a group of paid actors. You could set up any number of mind bending horrors in the depth of that cave. It would be expensive and horribly inconvenient but all so worth it.
– Leave strange signs of possible human habitation in a cave area, Stone bowls and knives. Bones and scraps of unknown animal. Freak them out. Have a group of men strip down, cover themselves in white chalky substance, milky white contacts, and carry stone spears. Appear around one of the corners deep in the cave. Shouting in an alien tongue.
– A small, very well kept child in formal clothing. Perfect English and manners. Coached to provide as little information as possible as why he is down there. He forgets or doesn’t know. Just insisting he wants to get back to the surface. Carries a small book with him. Like a Bible but it preaches an archaic message of some hateful demon worshiping religion. Little boys lets slip at some point some creepy shit. “Thank you for inviting me to your world, I can’t wait to make it a place a torment”.
– Old German men in tattered Nazi uniforms. (make sure none of their party speaks German).
– Figures in bio-hazard suits shining lights at their party in a massive cavern. Then quickly disappearing while leaving behind notes to turn back.
Yeah its cliche but so are all my ideas. It is the fucking unreal context of being 20 days into a underground expedition that makes it terrifying.