Miles from the ocean, there's diving beneath the streets of Budapest

Generally speaking, these are rare events in both sports but one allows much more time for rescues.

While spelunking, if you become lost or trapped, how long can you live without food (assuming your clothing is reasonably warm enough to protect you from hypothermia) while waiting for rescue? Quite a while, many days even. Most navegable caves have plentiful air and it being toxic isn't too common. Water is also usually present; it might not be clean water, but you won't easily die of dehydration in just a couple days at least.

Now imagine being trapped in a submerged cave, where none of the above applies at all, and you will die in a very specific range of seconds immediately after your extremely limited supply of tank air runs out.

Yep.

Also, silt lifting in submerged caves can reduce visibility down to a total zero in just seconds if you or a partner accidentally upset settled silt deposits with any sort of rapid movement. These can take more hours to clear than you have air to breathe, and in those situations, you'd better hope you have a guide line and absolutely do not let go of it at all.

Spelunking is very dangerous at its more extreme end (being the first to explore unmapped caves, going on multi-day trips into caves prone to flooding or other additional dangers, etc), but even normal cave diving makes it look like a sunday walk in the park.

I've seen many reports of utterly professional, extremely experienced cave divers dying during their descents despite doing everything they could think to do correctly. It can just be that dangerous. In some cases, this happens even in well-mapped underwater caves, and in a grotesque irony, there are many cases of them dying while working retreival operations for the bodies of other cave divers who just recently died in the same cave.

I think what happens next, if you get deep enough into the sport, is that you become good at it and you are looking for stronger challenges to overcome yourself again and again. That's how you become a cave diver.

Still there are some special places down in the caves as well. And I think what makes them even more specials for the divers is the feeling of exclusivity that most people would never get to go there.

It's also really peaceful underground.

Amusingly enough, I can't handle blue-water or wall dives (vertigo), nor wrecks (those aren't supposed to be there!), but caves are no problem. You've got walls, floor, and ceiling as a frame of reference, and everything is nice and cozy. It's like the Earth is giving you a hug.

[0]: https://commons.m.wikimedia.org/wiki/File:Vortex_Spring_cave...

For me it was a BHAG (Big, Hairy, Audacious Goal), and I'm glad it kindof helped change or tighten my trajectory. SCUBA training is designed for you to succeed, and supposedly if you make it past your first 10 dives, you're much less likely to have any severe issues. For danger, each dive is equivalent to walking ~100 miles or biking ~50 miles: https://en.wikipedia.org/wiki/Micromort#Leisure_and_sport

Some of the caverns are basically exactly like that scene from Star Wars where they land the Millenium Falcon in the mouth of the worm on the asteroid. It's pitch black, only your light is beaming around, there's little tiny flecks of "dust" in the absolutely clear water that you're floating in (seriously! it's like rain-water filtered through 50ft of limestone that's mostly undisturbed for centuries). Safe-ish if you're not dumb with a not-dumb buddy/guide, and focus on minimal impact. Take only memories, leave only bubbles.

There's a bit of a "science" component where you can see fossil remnants, or weird little fishies swimming around, and it is absolutely foreign, alien, and peaceful. I've experienced "halocline" (salt water under rain water, https://www.cenotetours.com/wp-content/uploads/2020/05/haloc... ) and thermocline (a coherent warm water "stream" flowing through regular water), seen turtles, puffer fish, sharks, urchins, octopus, and starfish (not in caves though!).

It's been years since I've done it, and I'd go through training/refresher again if I wanted to get back into it, and I'd really avoid "cave" diving (stupid tourist cavern routes that have 20-50 people per day are totally fine by me). It's a unique experience that supplements the general one (think: rock climbing / bouldering as an adjunct to hiking... "wow, I can do that too!")

In sports like skydiving and technical cave/wreck diving people often assume you get an adrenaline rush doing it and that’s what draws people in.

Not the case (for me at least).

Rather, when you get good enough to be competent at these there’s no adrenaline. Adrenaline is when you are operating beyond your skill level. The satisfaction comes from calm, cool, collected execution, with the knowledge and training that allows you to avoid the dangers and do something exceptional with a much lower risk profile than an outsider would assume.

It’s also fun to play with gear (toys).