Cave diver here, the article asserts how rare warm caves are but I think that is a very European mindset.
The Mecca for cave diving is in the Yucatán and surrounding areas and the caves there are exceptionally warm. The surface water can be chilly, coming in around 21c at one of the many cenotes (sinkholes, which are the entry points into the system) as rainwater fills them, but the further into the cave you penetrate you will eventually cross the halocline, at which point deeper = warmer ocean water. It’s quite unintuitive but delightful to warm up after a 2+ hour dive. It’s common for divers to go deeper, pull their wetsuit open a little to fill it with warmer water (24c+) and then rise up back to the planned depth.
Cold cave diving is a very different experience and is usually found in Florida and Europe. Don’t recommend.
Recreational (not caves, no thank you!) diver here, jealous of your balmy 21C=70F water temps.
Here in lakes Michigan and Superior, diving on wrecks usually brings you below the thermocline to water temps from 0C to 10C ~= 50F. Only on rare inversions or at the surface at the south end of the lakes do water temps get much above 70.
You Florida, Carribean, and Central American divers have it made with your balmy water temperatures!
I found Florida's caves positively delightful at 21 C; never felt the need to dive dry.
I am envious of the speleothems in Yucatán cenotes. Florida's caves are all phreatic, so you don't get any real decoration beyond scalloping. Still fun to dive, just not much to see aside from water, wet rocks, and a line. And not even that if you blow the viz.
21c sounds nice but I know Floridas geology leads to some comparatively deep caves. Most Cenotes range between 15ft-65ft but from what I hear about the Florida landscape is 85ft is average and some caves go past 300ft, which isn’t going to be warm anywhere.
My father used to be a technical cave diver. There are plenty of beautiful diving places inland. For example the Dubnik opal mines, which are not so far from Budapest.
I'm proud of him, but I'm very glad that he's not doing it anymore. If something happens or if someone panics down in the cave then it's easy to stir up the mud and loose your guideline. It takes just a moment, but when it happens it is super serious and dangerous to everyone in the expedition.
I recall seeing a clip of an interviewee who is a cave diver. He was giving a description of the time he came closest to death while cave diving, and it came down to someone in his group losing it, and him attempting to prevent that person's death, and then being stuck without a guide line and functionally blind in a muddy cave underwater after the person freaking out sped out of the cave. He said he was able to get out by slowly crawling back and forth upside down on the surface of the cave with his face pressed against it trying to find a thin crack he remembered led back to the surface.
What struck me the most was him saying "calm the f down cowboy, calm the f down or you're going to die", and his face when he said it. I can't imagine the sangfroid required. I also can't imagine the conversation when they both reached the surface.
Such a scary thing to do (tho in a sense possibly comforting like a return to the womb, or being interred -- in Mother Earth). Isn't the guideline karabinered to your suit, or you just "hold a thin thread in the dark"?
No, there are no lines attached (to minimise the risk of entanglement). In good visibility with pre-laid lines, you'll often not touch the line.
In poor visibility you'll gently hold the line. If there isn't a pre-laid line, the lead diver will have a reel which they progressively release, and tie-off at intervals (to any useful protrusion).
I met a cave diver recently. Dude is retired now but ran a consultancy for decades through which he and his team would go in and map previously unexplored caves (or someone had died trying).
He was a chill guy but like ... he was just steely af. Can't imagine the nerve it takes to crawl around in those places. Gives me the willies!
My first cavern dive was with a VERY experienced cave cartographer (Yucatan Cenotes, https://www.filoariannadive.com/alex.html ). Cavern is where technically "you can see the light", but if you turn a corner and can't see the surface then it converts into "cave" diving.
For the rank amateur that I was, being able to turn around, orient myself and see a sliver of light ~100ft behind me... yeah, "technically a cavern dive".
I tried to do a "buddy check" w/ him before beginning the dive and he almost pushed me away... the stories of him diving with side-by-side tanks, then pushing each of them through a gap in front of him, one by one, and then wriggling his body through. :insert-shocked-emoji:
Always remember: "Are you a diver, or a dummy?" ...what would a DIVER do? [don't panic, fall back to your training] Good to have that sense of self an security in lots of cases!
You've got to be extremely detail oriented, precise, and disciplined to do it right. I've got a friend who does it and I support him on his dives(hauling gear, etc) but I have zero interest and am not cut from that kind of cloth. Give me tight, muddy, cold, AIR FILLED caves any day though.
I truly don't understand the appeal. What is enjoyable about this experience? I like risky and athletic stuff and have done a bit of climbing (nothing technical) and the appeal there seems quite obvious - in addition to the adrenaline rush, you've got clean air, beautiful vistas and scenery, etc. A pitch-black, dank hole in the ground - ugh. The thought of getting lost, especially getting lost and losing illumination, seems like the ultimate nightmare. On the plus side, those big caverns with various mineral formations do look quite spectacular. But you tell me, what's fun about this?
For me, it was the challenge and allure of doing something relatively difficult and rare. The first time I saw a Stop - Prevent Your Death sign[0] at depth, I knew I wanted the training to go beyond it.
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.
I've done a few (~5-10?) cavern dives in the Yucatan, kindof on a dare/challenge. I met a man who said "I've always wanted to go cave diving in the Yucatan, it looks so beautiful and peaceful, you should try it!" ...and I did, probably within the year.
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.
Cave diving is about the only remaining way for an ordinary middle-class person to do original exploration. There is still a lot of virgin cave in some areas so it's possible to go places where literally no human has ever been before. Sheck Exley, one of the most accomplished cave explorers, was a high school math teacher in Florida. As one other explorer put it, literally more people have been to the Moon than have reached the end of the line in the Wakulla Springs underwater cave system.
Open water diving around coral reefs and shipwrecks is simply beautiful. (Maybe sadly now less-so than it used to be.) Divers love to spend time down there in a weightless state.
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.
I’d argue much safer as your upper bound is not an air reservoir strapped to your body, it’s food/water …or in the event that shit really hits the fan, how fast you can secure a wound.
Generally speaking, these are rare events in both sports but one allows much more time for rescues.
"Some of the best diving I've ever done is snorkeling in Cancun..."
You're on the surface, generally with a life vest, don't have to worry about running out of air, generally the guides inter-communicate and take you to hot spots of fishes or turtles or whatever... tropical warm water. Biggest difference is access to air rather than having to be "self-sufficient".
I recently took a cave rope climbing technique course, after being comfortable with rope climbing in other disciplines, such as climbing, rope rescue and glacier rescue.
The bolting techniques used in caves are fucking terrifying. They work, but they are terrifying.
I don't understand, if you are not sure about a two bolt anchor, you can always drill more, rock quality is usually very good. Why do you trust, say an ice axe deadman more than expansion bolts?
I'm specifically thinking about using older self-drive bolts, which seem to still be used if they are placed. I have only met people thinking they are acceptable in the caving environment.
And also using temporary bolts as the Coeur 8 mm, which is rated for 2 kN before deformation in the worst direction (and the mechanism of those bolts are more akin to a cam, making them squiggle a lot in the hole, which is safe, but scary. My ice axe don't squiggle).
Obviously you use redundant bolts, and there are much lower forces in SRT than in dynamic falls, but I still think it's scary as hell.
Here are a few things to keep in mind in asking that question:
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 don't think I'd like it. The jump scare potential and idea of being caught underground in something that could collapse is not appealing. My thing would more probably be trying experimental gas mixtures for weird technical diving feats, if I were into any of that at all.
I'm wary of cave diving because of the safety issues, but this feels like one I would do. With the fairly controlled environment, warm waters, and guide lines, it feels like about the safest cave dive you can do!
I grew up pretty spoiled by riches, being certified in the Caribbean, but diving quickly lost its allure to me. You start losing color quickly at depth and it’s like staring into an aquarium while risking your life.
Are the tanks still 40lbs or has technology finally caught up to them?
Tanks haven't really changed, although I don't know why anyone would be concerned over 40lbs. What has really improved are dive lights. You can get LED primary lights now that are quite bright with excellent battery life so you can see all the colors.
This whole thread gave me anxiety. I wonder if some kind of heads up display could show divers a map of where they've been and help orient them in silt visibility situations.
Bypass paywall - https://archive.ph/gGHzh
Cave diver here, the article asserts how rare warm caves are but I think that is a very European mindset.
The Mecca for cave diving is in the Yucatán and surrounding areas and the caves there are exceptionally warm. The surface water can be chilly, coming in around 21c at one of the many cenotes (sinkholes, which are the entry points into the system) as rainwater fills them, but the further into the cave you penetrate you will eventually cross the halocline, at which point deeper = warmer ocean water. It’s quite unintuitive but delightful to warm up after a 2+ hour dive. It’s common for divers to go deeper, pull their wetsuit open a little to fill it with warmer water (24c+) and then rise up back to the planned depth.
Cold cave diving is a very different experience and is usually found in Florida and Europe. Don’t recommend.
Recreational (not caves, no thank you!) diver here, jealous of your balmy 21C=70F water temps.
Here in lakes Michigan and Superior, diving on wrecks usually brings you below the thermocline to water temps from 0C to 10C ~= 50F. Only on rare inversions or at the surface at the south end of the lakes do water temps get much above 70.
You Florida, Carribean, and Central American divers have it made with your balmy water temperatures!
I found Florida's caves positively delightful at 21 C; never felt the need to dive dry.
I am envious of the speleothems in Yucatán cenotes. Florida's caves are all phreatic, so you don't get any real decoration beyond scalloping. Still fun to dive, just not much to see aside from water, wet rocks, and a line. And not even that if you blow the viz.
21c sounds nice but I know Floridas geology leads to some comparatively deep caves. Most Cenotes range between 15ft-65ft but from what I hear about the Florida landscape is 85ft is average and some caves go past 300ft, which isn’t going to be warm anywhere.
My father used to be a technical cave diver. There are plenty of beautiful diving places inland. For example the Dubnik opal mines, which are not so far from Budapest.
I'm proud of him, but I'm very glad that he's not doing it anymore. If something happens or if someone panics down in the cave then it's easy to stir up the mud and loose your guideline. It takes just a moment, but when it happens it is super serious and dangerous to everyone in the expedition.
I recall seeing a clip of an interviewee who is a cave diver. He was giving a description of the time he came closest to death while cave diving, and it came down to someone in his group losing it, and him attempting to prevent that person's death, and then being stuck without a guide line and functionally blind in a muddy cave underwater after the person freaking out sped out of the cave. He said he was able to get out by slowly crawling back and forth upside down on the surface of the cave with his face pressed against it trying to find a thin crack he remembered led back to the surface.
What struck me the most was him saying "calm the f down cowboy, calm the f down or you're going to die", and his face when he said it. I can't imagine the sangfroid required. I also can't imagine the conversation when they both reached the surface.
https://www.youtube.com/watch?v=or92IMcLoIc clip for anyone interested. Gripping stuff.
Such a scary thing to do (tho in a sense possibly comforting like a return to the womb, or being interred -- in Mother Earth). Isn't the guideline karabinered to your suit, or you just "hold a thin thread in the dark"?
In poor visibility you'll gently hold the line. If there isn't a pre-laid line, the lead diver will have a reel which they progressively release, and tie-off at intervals (to any useful protrusion).
https://divingadelaide.com.au/basic-reel-and-guideline-use-f...
Even caves have weather
I met a cave diver recently. Dude is retired now but ran a consultancy for decades through which he and his team would go in and map previously unexplored caves (or someone had died trying).
He was a chill guy but like ... he was just steely af. Can't imagine the nerve it takes to crawl around in those places. Gives me the willies!
My first cavern dive was with a VERY experienced cave cartographer (Yucatan Cenotes, https://www.filoariannadive.com/alex.html ). Cavern is where technically "you can see the light", but if you turn a corner and can't see the surface then it converts into "cave" diving.
For the rank amateur that I was, being able to turn around, orient myself and see a sliver of light ~100ft behind me... yeah, "technically a cavern dive".
I tried to do a "buddy check" w/ him before beginning the dive and he almost pushed me away... the stories of him diving with side-by-side tanks, then pushing each of them through a gap in front of him, one by one, and then wriggling his body through. :insert-shocked-emoji:
Always remember: "Are you a diver, or a dummy?" ...what would a DIVER do? [don't panic, fall back to your training] Good to have that sense of self an security in lots of cases!
also https://bonneterremine.com/ near St Louis.
"The World's Largest Subterranean Lake Is A Vibrant Scuba Diving Paradise In Missouri"
Only in my most terrifying nightmares do I find myself cave diving. Kudos to those who enjoy it.
You've got to be extremely detail oriented, precise, and disciplined to do it right. I've got a friend who does it and I support him on his dives(hauling gear, etc) but I have zero interest and am not cut from that kind of cloth. Give me tight, muddy, cold, AIR FILLED caves any day though.
I truly don't understand the appeal. What is enjoyable about this experience? I like risky and athletic stuff and have done a bit of climbing (nothing technical) and the appeal there seems quite obvious - in addition to the adrenaline rush, you've got clean air, beautiful vistas and scenery, etc. A pitch-black, dank hole in the ground - ugh. The thought of getting lost, especially getting lost and losing illumination, seems like the ultimate nightmare. On the plus side, those big caverns with various mineral formations do look quite spectacular. But you tell me, what's fun about this?
For me, it was the challenge and allure of doing something relatively difficult and rare. The first time I saw a Stop - Prevent Your Death sign[0] at depth, I knew I wanted the training to go beyond it.
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...
I've done a few (~5-10?) cavern dives in the Yucatan, kindof on a dare/challenge. I met a man who said "I've always wanted to go cave diving in the Yucatan, it looks so beautiful and peaceful, you should try it!" ...and I did, probably within the year.
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!")
It’s really fun to be good at something.
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).
Cave diving is about the only remaining way for an ordinary middle-class person to do original exploration. There is still a lot of virgin cave in some areas so it's possible to go places where literally no human has ever been before. Sheck Exley, one of the most accomplished cave explorers, was a high school math teacher in Florida. As one other explorer put it, literally more people have been to the Moon than have reached the end of the line in the Wakulla Springs underwater cave system.
Open water diving around coral reefs and shipwrecks is simply beautiful. (Maybe sadly now less-so than it used to be.) Divers love to spend time down there in a weightless state.
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.
I’m detail oriented which is exactly why I’m unwilling to bet my life on not missing a detail.
how much safer is normal cave spelunking? I hear about accidents pretty often with that too, or getting into a crevice you can't back out of...
I’d argue much safer as your upper bound is not an air reservoir strapped to your body, it’s food/water …or in the event that shit really hits the fan, how fast you can secure a wound.
Generally speaking, these are rare events in both sports but one allows much more time for rescues.
"Some of the best diving I've ever done is snorkeling in Cancun..."
You're on the surface, generally with a life vest, don't have to worry about running out of air, generally the guides inter-communicate and take you to hot spots of fishes or turtles or whatever... tropical warm water. Biggest difference is access to air rather than having to be "self-sufficient".
What about the weird gases that can be in caves? Or just gravity dropping you down a hole? Sounds pretty dangerous.
I recently took a cave rope climbing technique course, after being comfortable with rope climbing in other disciplines, such as climbing, rope rescue and glacier rescue.
The bolting techniques used in caves are fucking terrifying. They work, but they are terrifying.
I don't understand, if you are not sure about a two bolt anchor, you can always drill more, rock quality is usually very good. Why do you trust, say an ice axe deadman more than expansion bolts?
I'm specifically thinking about using older self-drive bolts, which seem to still be used if they are placed. I have only met people thinking they are acceptable in the caving environment.
And also using temporary bolts as the Coeur 8 mm, which is rated for 2 kN before deformation in the worst direction (and the mechanism of those bolts are more akin to a cam, making them squiggle a lot in the hole, which is safe, but scary. My ice axe don't squiggle).
Obviously you use redundant bolts, and there are much lower forces in SRT than in dynamic falls, but I still think it's scary as hell.
The strapped air reservoir could come in handy for when it rains...
Much safer. Spelunking can be fairly safe if done with caution and an experienced team. Cave diving causes fatalities even among experts.
And just to labour the point some more, the experts that are sent to recover the bodies of the experts that have passed have also ended up dead.
Here are a few things to keep in mind in asking that question:
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 don't think I'd like it. The jump scare potential and idea of being caught underground in something that could collapse is not appealing. My thing would more probably be trying experimental gas mixtures for weird technical diving feats, if I were into any of that at all.
I'm wary of cave diving because of the safety issues, but this feels like one I would do. With the fairly controlled environment, warm waters, and guide lines, it feels like about the safest cave dive you can do!
I grew up pretty spoiled by riches, being certified in the Caribbean, but diving quickly lost its allure to me. You start losing color quickly at depth and it’s like staring into an aquarium while risking your life.
Are the tanks still 40lbs or has technology finally caught up to them?
Still steel (or sometimes aluminium) and heavy. Carbon-fibre tanks are still extremely esoteric and rare in diving.
There's also not much point to making tanks lighter, since you need weight anyway to counteract the buoyancy of the air, your wetsuit, etc.
Tanks haven't really changed, although I don't know why anyone would be concerned over 40lbs. What has really improved are dive lights. You can get LED primary lights now that are quite bright with excellent battery life so you can see all the colors.
https://halcyon.net/products/focus-2-0-primary-light-corded
I was concerned because I was mostly shore diving. I hadn’t considered LEDs being used for dive lights and appreciate the link.
I've done shore dives with double tanks that weigh over 100lbs. Seriously 40lbs is nothing to be concerned about.
This whole thread gave me anxiety. I wonder if some kind of heads up display could show divers a map of where they've been and help orient them in silt visibility situations.
_Miles_ from the ocean? Budapest is 620 miles from the nearest ocean at the mouth of Elbe.
(Incidentally exactly 1000 km.)
Made that same comment to friends when I first came across the article.
Technically correct, I guess: it is miles (quite many of them).