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Safety Training for Overhead Environments

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Well-Known Member
Jul 29, 2001
Seeking Training for Overhead Environments

I am interested in information and information sources on freediving techniques and safety for overhead environments. I am specifically interested in cavern (not cave) freediving and wreck diving.

I find plenty of information and training available for SCUBA diving overhead environments, but it seems to me that a different set of considerations must apply to diving on a single breath with a buddy who has but one breath to use in helping should a problem arise.

Thanks in Advance for advice and discussion.
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So I´m not the only one nuts enough to freedive caves and tunnels, huh. Glad to hear it, they were making me wonder about myself.
What is the difference between caves and caverns?
Where do you do this. I live on Isla Mujeres, Mexico, where the bottom is a Swiss cheese of different size holes and caves and such. Exhilerating.
You just might find, as I have found in other activities I like, that there isn´t much written down--we have to figure it out for ourselves.
I don´t want to patronize if you{re way ahead of me on all this, but a few tips I´ve been panicked into:

--If things get weird, roll over on your back. You might be able to just crawl out along the top of the cave.

--Spend some time learning the "Objects may appear larger than they really are" thing, new estimates of size/distance. It really sucks to commit to a tunnel, then find out the exit hole is smaller than you thought. Especially since fins dont come with Reverse. (It there is a way to back up, tell me about it)

--You are most like to bang a big hole in your head when coming out. Maybe its just me, maybe its that suddenly ascending instead of just feeling your way through, maybe its getting air fever and not looking up enough as you come out of a hole, but that seems to be where I get really scraped up.

--Underwater dings, at least around here, dont heal right. There is some enzyme or something that makes cuts heal slowly and rash up, If anybody knows about this, Id love to hear it. Neosporin works sometimes.

--Do you think weight belts are a good idea for this stuff? I dont use them, but sometimes wonder if theyd be a good idea.

--Do we really have some sort of deathwish to do this, or are we just exploratory athletes trying to do something new and challenging?
Not alone down there after all

Ahh, finally some replies!!! I was beginning to think I had either asked such a stupid question that no one took me seriously, or that my buddy and I were, indeed, the only cavern enthusiasts.

We dive in the spring caverns in north central Florida, USA. Many are along the Sante Fe and Suwannee rivers; some are further south toward the Gulf of Mexico at Crystal River, etc. Swiss-cheese limestone; 72 degree crystal clear water. Fantastic!

I'm very excited about the possibility of getting a more in-depth discussion going on this topic, and maybe even developing some kind of "rule-book" of safety.

I have searched long and hard for specific information about free diving in overhead environments (ohe), but have found nothing yet. I’ll keep looking – I have several books on order that many of you have probably already read. - maybe there is something in FreeDive or another book??

First, just to make sure we are using the terms the same way, caverns vs caves:

Caverns are spaces where you can see the daylight, at least through the opening. You may need a light to swim around the cavern (to see all the beautiful formations, and the fish, and to keep from hitting your head on rocks & such), but you can find your way out of a cavern without a light because the daylight coming through the entrance is always visible.

A cave is a passage totally beyond the sight of daylight. If your light fails or you kick up too much silt for your light to illuminate the cave passage out, you’re in big trouble!

Personally, I stick with caverns. I have a good life up here in the air, and the danger of free diving into true caves are too substantial for me to risk.

It seems to me the risks of cavern freediving can be mitigated to such an extent that it can be done relatively safely if a person exercises some caution, judgment and restraint. Personally, I have too much fear not to use caution and restraint.

I’ll give my (perceived) list of dangers in order of most to least likely, and ask others to comment, disagree, modify, etc.

1) Hitting your head. This is a serious problem because it can mean the difference between getting out or not.

2) Shallow Water Blackout; not unique to overhead environments (ohe), but perhaps more of a danger here because you have to leave plenty of time not only to get up, but first out from the ohe and then up.

3) Passing out with overhead restriction between you and the surface. This is less likely than #2, but more serious if it occurs because of the complications it causes your buddy in getting you back to air.

4) Getting stuck or caught on something. Usually, fishline is not a problem, but I’ve seen iron bars from signs left by cave divers. Limbs from sunken trees, sharp rocks that could snag a wetsuit, and other debris that could looks like a potential problem.

5) Getting lost or silting up the space so badly that the way out is not clear, or becoming badly disoriented.

Here are our Precautions, in no particular order of importance:

a) Carry a good light, maybe even a backup, and shine it ahead of you as you move – you’re less likely to smack into something you can see;

b) Swim with one hand always in front of you to feel for protrusions that might knock you out if you don’t happen to see them and hit them;

c) Wear a neoprene hood or helmet,

d) Dive by time, not by feel. If your limit is 90 seconds downtime, don’t vary that until you’ve practiced in an open water system and know you have increased your conditioning and your total apnea capacity.

e) ALWAYS dive with a competent buddy. This is NO time for solo, period.

f) NEVER push your physiological limits in an ohe! Use training to increase your limits, but stay well within your limits in an ohe. Always have 25 – 30% left. In other words, if you can do 4 minutes in the open, never go longer than 3 in ohe.

g) Plan EACH dive, and make sure your buddy knows the plan, including the goal of the dive, where the diver is going in the cavern, how long he will stay, and any other special features of the attempt.

h) Explore caverns incrementally. Push into the cavern a few more feet each dive. Take your time getting to know the cavern a few feet at a time. After all, the joy is in discovery, so make it last. Don’t try to reach the back wall of a 40-foot room the second time you go in. Taking it slow helps you maintain your orientation and confidence should something go wrong.

i) Buddies are spotters, not companions. Two divers out of air are worse than one. The buddy should trail the diver by a pre-arranged time period, and should stay near the exit until the diver comes past him on the way out. This ensures that the buddy is oriented in the cavern and has the oxygen reserve to assist if a problem occurs, or can quickly bolt back to the surface to shout for help and then head right back down to assist.

j) If possible, dive where competent topside help is readily available should the buddy have to shout for help. Although I aim never to have to test it, underwater rescue from ohe, then cpr , emergency medical treatment, and ambulance driving are too much to ask of one person.

k) weight yourself to be neutral in the cavern. If it is deep, that may not require much weight. (I use about 1 kilogram). The last thing you want is to be fighting to stay off the ceiling - that can be dangerous.

OK, if you've read this far, you're probably interested enough in this subject to post a reply.
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Reactions: abdessalam

Enjoyed reading your repsonse and appreciate your efforts in trying to obtain more info on cave/cavern freediving. For the sake of others who may be interested, I'm copying a portion of the e-mail that I privately sent you:

"I much prefer deep springs over the cave diving. Little River and
Olson are somewhat exceptions due to the large open caves. Getting back into small caves (against the spring flow) and turning around with big fins is often too risky for me. I usually only go in as far as I feel comfortable and then just practice static instead of pushing myself to go further. Several things work against me in the spring caves (in addition to potentially cramped spaces): I am usually fighting a strong current, which uses up my oxygen; as I get further away from daylight (I do use a flashlight), my heart begins to beat faster (fear) and thus using my oxygen; and, since I usually don't wear weights, I have to fight from floating to the top of the cavern (and hitting body parts against the hard/sharp limestone) and thus, again, using my oxygen. I have never used a reel as I really never go in far enough to feel the need for it (I would really be pushing myself to go in that far). Springs with low flow are more likely to silt-up and thus more dangerous (Royal Springs would be a good example - didn't 2 divers die there several month ago?). I go
to the bottom of Royal (50') but don't go in. "

I look forward to learning more and getting other opinions in this area.


P.S. Until you explained in your post, I too was fuzzy on the distintion between caves and caverns. Is this your own distinction or is it generally recognized?
Christ, I thought I was nuts.
So to caverns and caves could I add the term "tunnel", being simply a tube with entrance and exit? That's what we call it, anyway.
Despite a lot of criticism and hysteria in this area, I dig the activity and consider it a "because it's there" think like climbing. I'm still feeling my way through being able to judge whether I can make it through a given distance and how that changes at different depths.
What's frustrating to me in the Mexican Caribbean area with it;s swiss cheese bottom structure, is seeing layers of holes descending and knowing that I can't possibly get down to the daylight below, or that the possibility of dying trying is prohibitively high. But nobody wearing tanks could get into the crevices at all, so I guess we aren't going to explore these places. (One thing I dig about this stuff is that it is impossible for scuba divers)
Or maybe it's just that I see something I can get through and have to give it a shot. Maybe it's a guy thing?
I do this almost exclusively solo, because that's the way it goes. Not that I'm arguing with your statement thats it not such a good idea.
Frankly I find fishline and net to be a major scare. Especially if you're in something to small to get your arms up and cut it. Do you have some cool way of spotting or dealing with monofiliament? That's another thing that changes at depths. At 20 feet you have time to screw around with a snarl of line and hooks, at 40 feet things get hairy in a hurry.

By the way, I met a scuba guy in the Bahamas who goes down hundreds of feet into holes and caves, lugging six tanks with him and leaving them for his return trip. He may be a tanker, but he's an admirable lunatic in my book.
More power to you . . .


I don't mean to be critical or to imply that you or anyone else is "nuts" for taking any risk they feel is warranted and worthwhile. I certainly do not advocate restricting anyone who wants to take a risk that does not imperil others. We do a lot of that in the US, but I'm not a supporter of it.

It sounds as if you are doing some adventurous things, and I wish you all the best in doing it. Keep us posted - it's exciting stuff. I'm not in a position to do that personally (too many dependents), but I can enjoy other's experiences vicariously.

Rather than being critical of others or trying to be somebody's mom, my interest is in identifying the various things that can go wrong freediving into an ohe, and then formulating precautions to eliminate, minimize, or prepare to deal with those problems should they occur. It's up to each individual to decide how much precaution they want to employ, but it's hard to make good decisions if you don't understand what can go wrong. I'm fairly inexperienced, so I have a lot to learn from folks like you who have been doing this for a while and know first hand what can go wrong.

Thanks for the warning about monofilament. I have not encountered it in the places I dive, but many of those prohibit fishing. I don't have any good suggestions for spotting monofilament line in a restricted space, but I hope someone else does as this is obviously a bigger problem than I appreciated initially.

Regarding "cavern," "cave," "tunnel," etc., I'm not trying to be pedantic, just employing the terms I thought were officially adopted by cavers. I got them from the cave diving books and websites. I don't know if cavers make a distinction between tunnel and cave, but "tunnel" is pretty descriptive - I think it's definitely more of a challenge than the stuff I do!


There's also some very interesting info and good links on some of these web sites. I know cavers (scuba) who remove their tanks so they can push them ahead into tight passages (tunnels). Bummer if you drop your tank down a hole, I suppose. Bubble blowers can get cavern and then cave certified, but I don't think much of their training would be useful for us because most of it involves navigation, exotic gases, decompression, etc. We don't have time for that on one breath of air.

OK, so please use your experience to help out us beginners . . .

What kind of lights do you carry? In the places you dive, do you have to worry about silting out a passage and losing visibility? If so, how do you handle silting up the way out? Do you trail a line to find your way back out? Do you use long fins, or are the places you dive too restricted to turn around with long fins on? Do long fins make it tough to prevent silting up the tunnel?
I continue to be intrigued by what your doing (and appreciate your non-Mom attitude and wish everybody was less judgemental, including me). I hope to discuss some of this more with you when I am not traveling around.
It sounds like we are doing different stuff in different environments. Silting is not a problem where I am, it's pretty much stone and sand bottom, open sea. Most of the spaces I enter, turning around is not much of an option--but you can see daylight.
What depth are you doing this at? And here's what I keep wondering about...if you are going into blind caverns, how do you know you know you can get out alive? Are they checked out first using tanks? Mapped? You don't sound like a guy who would just head into a dark cave hoping to find a connection before his air runs out. (Neither am I) What time elapse is involved here?
Yeah, I really should wear a helmet, I guess. I've taken several nasty head cuts this year, and more on shoulders. But I don't generally go out intending to cave--I usually just run into something that looks interesting, check it out, and go for it. Since I dive alone, I tend to err on the chicken side. (Most of the time--hell I'm over fifty and a total wreck, so I don't mind dying :)
Now I realize we are diving different environments, indeed. I am diving in the freshwater springs of north central Florida, not in saltwater. No tides or other currents to consider. Here, the limestone rock bed is like swiss cheese. Sometimes, the rock crumbles from the surface, and a sink or spring is created. The springs are where water wells up from below; a sink is where the opposite occurs. Hydrology determines the difference, but I'm no geologist, so can't explain why/how. It's essentially diving into our groundwater - drinking water - same place our wells sucks from.

Many of the springs / sinks turn out to be surface connections to a larger network of tunnels, rooms, etc. in the groundwater. Some go on hundreds of feet vertically and thousands horizontally - underground rivers, really. Nearly all of these have been explored by cave divers, and maps exist for most.

In some places. rivers disappear underground and then reaappear miles later. When you get a chance, look at some of the sites I posted earlier to get an idea of what I'm talking about. The Yucatan also has many of the same types of formations, and world record depth cave dives have been set there. Also, check out <http://www.cdc.net/~rling/caving/exley.htm>, a eulogy for a local school teacher considered one of the very the best cave divers ever - truly a world class explorer.

The water in springs is incredibly clear - paradise-like. These are places of phenomenal beauty - constant 70 -73 degree F. water year round. The springs give rise to many clear water surface rivers; some of the springs issue 50 - 80 million of gallons of freshwater per day - quite a flow to fin against.

We've thus far only tried diving springs (not siphons or sinks). However, we are just milling around in the fourier, so to speak, compared with exploring the mansion, as cavers do. Cavers worry about silt back in the far reaches of the tunnels (caves), but where we dive, the flow is high, the walls well cleared of silt by the flow, and the bottom rocky or course gravel. Maybe someday I'll try diving a sink or siphon (hole that alternates flow, sometimes a sink, other times a spring), but for now, I stick with high flow systems and do not go out of sight of daylight.

In the caverns, you can't always see the walls without a light, but you can always see the opening . . . unless you were to dive at night, of course. So there's not much chance of losing your way out. However, daylight at the entrance can often be seen from 100 feet or more back in a cavern, so if our lungs and guts are big enough, we could be a long way from a straight shot to the surface even though the way out is in plain sight.

We dive into caverns of various depth. Some are but 15 feet below the surface; others 40 - 50 ft. Others are more, but I haven't the guts to try those yet - need to know I am well within my limits before attempting something. So for us, it's not so much the depth as the distance we travel under the rock that concerns
us. As Scott mentioned earlier, we are swimming against a current on the descent, so that uses up a lot of O2 unlike going straight down.

So far, we dive only into fairly large rooms, so turning around has not been a problem. However, I am constantly mindful of restrictions because turning around in a tight space could use lots of O2 quickly. Also, I would worry about getting snagged on a sharp rock or tree root - some tree roots can grow into the rock many feet below the surface.

It seems to me we are not doing anything terribly dangerous, but the scuba cave instructors in the area - this is a big area for cave diving - act as if this is completely crazy, and say we should not go more than a few feet under any ledge without open water and then cavern scuba certification.

Of course, I've yet to find any of the scuba folks who really free dive, though many claim they are good at it because they occasionally go down without a tank to free an anchor or check out a reef to see if there are fish before going down with tanks to spear fish. I don't get the impression that any of them actually spend enough time diving without a tank to get comfortable with it. I may be wrong here, but I think most of them would be terrified without their prostheses - they concentrate on preparing their dive plan and their gear, not on their legs and lungs.

Scott, since JMD left the area, we may be the only others on the forum who fdive the Florida springs. We should rendevous sometime at a good spring and dive together for a while.
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cave, tunnel...under ice?

Hi ya fellas, you are really haveing a great post here going, I would like to try some of that too, especially those tunnels. Earlier you spoke about the safety when diveing in caves etc. I just want to tell you guys about stuff done up NORTH! when our sea freezes over you get pretty unique environment to dive in, water is clear and ice lets light through fine and there is no wawes to disturb your consentration...water is pretty cold though and 7-9mm suit would be a good idea, right..?:duh when diveing under ice number one rule is use a rope! when you dive under ice you can get lost under huge and thik layer of ice! that is the worst, ofcourse then comes the usual dive with buddy. ETC, but perhaps when diveing cavern rope would not be such a bad idea? Well Just wanted to share my experience.:D
rope diving

Diving under ice is something I've read about but never thought about actually doing it! How does the cold water affect your breath hold ability? I would think you would use so much O2 staying warm it would be tough to freedive at all.

I can uderstand that a guide rope is a must under the ice. Do you use a reel, as cave divers do? That must be eerie seeing light coming through ice, knowing the surface is near but inaccessible!

Do you have to worry about currents under the ice?

I've wondered if the flow coming out of some of our springs could pin a diver inside a cavern in a back eddy. In that case, being able to pull out on a rope would be very nice. I've wondered if the risk of getting disoriented or losing sight of the cavern entrance is greater than the risk of entanglement in a line. This is an element of our safety precautions I have not completely figured out yet.

Thanks for the reply - this is an interesting aspect of fdiving that I do not hear much about.
under ice...

Well I have not been diveing under ice, because of two things..I don't want to risk it and I don't have the gear to do it, since it is done with no less than 7mm wetsuit usually with drysuit though, but I have been swimming in such water a we drilled hole in ice and went swimming and let me tell you the freediveing would be short! water is so cold that your whole body seems to shrink and you use loads of oxygen just to stay "alive"..
I have been diveing up north in the rivers and lakes which came from glacier and that was pretty cool visibility was incredible, but there is not much to look at, but some fish if you get lucky. the diveing is bit different.
Usually my body starts shake because of the cold and then your diveing suffers, but you are still able to do it and it is worth it if you get the chance to try it out.
I don't think there is done diveing at all at rivers and at Baltic Sea there is little currents and if there is they are weak, so I don't think they are the problem.

See the "Florida Freedivers" thread under the buddy section - there are others out there. If you come to Central Florida, let me know and we'll hit Blue Springs. Otherwise, I'm due for a trip to Troy pretty soon and I'll be in touch.

DIving under ice. I love it. Not that I'd ever DO it--I hate cold water. But again, it's nice to run into others who like ot do stuff like this. (And don't take the advice of scubadubas on the matter).
Are you swimming in from the edge of the ice, or boring holes and jumping in like in Bugs Bunny Cartoons? Do you find air pockets under the ice to allow extended trips? (Like in all the movies when the guy's about to drown?)
Rope sounds like good idea under the ice all right. I doubt it would help much in tight caves and tunnels because you might get fouled in it and dragging you out would probably cheese-grater your hide.
If I was going to take peopled along on these things I might consider putting a rope hand-rail in place. Any sort of rescue in tight quarters like this would be virtually impossible.
Scott, do those rooms have stalactites or any such formations? I am getting the impresion now that you are talking about rather shallow depths, which explains having enough air for more extended trips.
shallow is a relative term

I'll let Scott answer for himself, but I know we dive some of the same sites.

The caverns I dive are accessed at depths of 10 to 50 feet, but some are deeper (the cavern opening at Wakulla Springs is at 180 feet, I believe - haven't gone into that one!). So, you dive down a ways - say 40 feet - and then into an opening in the rock that takes you into rooms or tunnels that usually descend further from there. At some point you are beyond sight of daylight, i.e., in a cave. I don't go that far. I like sites where the cavern is large and there is lots of room to explore within sight of the opening.

Some have stalactites and the like. The cave opening at Devil's Eye, for example, is in a hole about 20 feet deep (thus the name), and has many such formations at the opening.

Some of these places are incredibly beautiful, and there are catfish, gar, and eels lurking back in the dark. The water is crystal clear - it's like diving in air, it is so clear.


Christopher has answered quite eloquently and I so I defer to his response.


I've freedived under ice, and am going to do it again this winter, probably in November and December. I posted a couple of stories in the past. It's quite exciting. I found that throwong a weighted line in first is a good idea, so that you can move around away from the hole, but still be able to see your way out. Ice is invisible at the bottom 8 cm, and also indistinguishable from the hole if the ice is clear. I did it in a 5mm suit, the dives were around a minute to a minute and a half, with long breathe-ups. Cold definitely affects the duration. Cold water on your face is good for extending dives, but not when the rest of your body is cold. Come on snorklebum, I think you're getting soft down there in freedive paradise!
Erik Y.:( Brrrrr
ice tourism


Why do you do this? Is it for what you see below the ice? Do you spearfish under the ice? I would hope there are seals, or other fish - probably moving v e r r r r r r y s l o w w w w w l y at that temperature - that you go to see or hunt. Please don't tell us you do this just to stay in fdiving shape over the winter! -Or is it one of those things you have to try just because it is so extreme?

I think you could get Snorkelbum to join you if you told him there are ice tunnels for him to crawl into.
Re: ice tourism

Originally posted by cjborgert

Why do you do this

Haha! Shall I quote a certain famous mountain climber?
You might have noticed that I am very passionate about freediving....enough to go out on a 15F day and get under the ice at one of the lakes around here. I am 1200 km from the sea, and I take what I can get. I absolutely HATE swimmimg pools, but I go in them too, especially in the winter, when it's 25 or 30 below zero outside.
I am very envious of you guys down in Florida diving the springs. In the winter we usually have the best vis in the lakes, because there is no weather to affect them, so it's worth doing, for me. The only problem, as I wrote in a post earlier this year, is taking off the suit and looking between your legs. I don't care if you're Dirk Diggler, you will not be happy for a while!
:( Cheers,
Erik Y.

Erik my friend,

"Passionate" is not the word I would use, but my hat (or rather, my 7mm hood and double-lined fleece underhood) is off to you. Good luck.

[P.S. to the forum: We need to pitch in for a plane ticket to get this guy to warm water this winter! I'm worried about him!]
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