Caverns for beginners
Louise Trewavas gets her first taste of cavern diving on a training course in Menorca

Underwater caves, black tunnels with nowhere to surface just thinking about it is enough to induce a quiver of anxiety in even the most experienced diver. When I told my BSAC branch that I was going cavern diving in Menorca, the Diving Officer felt the temperature of my forehead and started to unpack the oxygen.
I explained to him the difference between caves and caverns: cave diving involves going a long way in where the sun dont shine, but with cavern diving you always stay within sight of the reassuring blue window that is your exit. Its cave diving for softies (or the sane, depending on your perspective). And the skills you learn are also very applicable to British diving conditions, particularly wreck penetration.
I assured my DO that I wasnt running off to dive in just any old cave with any old dodgy dive operator I was going in cavern with Gavin.
Gavin Newman is an action photographer and cave diver with more than 18 years experience, and I was going on a PADI-recognised cavern diving speciality course to be trained in how to survive in an overhead environment, with the promise of lots of fun dives in a wide range of spectacular caverns. At this point, the DO put the oxygen away and the Training Officer wished me well.
Ive never been to Menorca before, and Club SAlgar conjured up images of rampant 18-30s holidays, drunken excess and wet T-shirt competitions. How wrong can you be! Club SAlgar is in fact an upmarket villa resort with not a lager lout in sight. It has a friendly and well-equipped diving centre and more dive sites than you could shake a stick at.
Oh, but the Med its so fished out, everyone had warned me. Not a bit of it on my first dive I drift through a storm of feeding sergeant-major fish, in stunningly clear blue water at a diver-friendly 26ÂC, am practically knocked over by a frenzied shoal of silver seabream, and end up face to face with a large black and yellow speckled moray.
But isnt it all torches on your head and terribly tekkie I have to admit I had worried a bit about this one. But once I get there I find to my great relief that youre not required to wear a twinset a main torch and at least one back-up is all thats required, and additional gadgets are not just dis-couraged but actually removed from your kit.
The main emphasis is not on kit, but on techniques. Each morning we start off relaxing by the pool while Gavin gives a short lecture and explains the days diving and exercises. Then we get kitted up and set off for the dive site each day a new and different experience.
We practise many of the skills in open water before applying them inside the caverns. Gavin has laid out a guideline course around the reef that includes lots of difficult features. First we swim around and have a look at it, then take it in turns to put on a blacked-out mask and follow it blind you soon appreciate the difference between a nice clear belay and a sloppy mess of loose line and criss-crossing guides when youre fumbling your way around by touch alone.
And having experienced the perils, the reel is handed over to me to lay my own guideline maybe not quite such a simple task after all. It takes two hours of careful unpicking to sort it out and two days to live it down when I jam the reel.
Cavern diving involves lots of teamwork: one person on the reel, a buddy to help find belays and check the line, and a third person as back-up. That means planning the roles in advance and following them through.
We all have to closely monitor our air and make sure we dont use more than a third on the way in leaving a third to get out on, and a third for emergencies. And speaking of emergencies riding piggy-back style on your buddys cylinder while breathing off his octopus rig and wiggling your way through a restriction is quite an experience!
My favourite exercises were the anti-silting techniques. Its all about accurate buoyancy control, getting a good angle on your body, and then nice gentle fin strokes from the ankle. The results are immediately apparent when you return down the same passage. If you can still see, youre doing OK!
After one exercise, Gavin went through and deliberately kicked up the silt so we could experience zero viz in a cave. While this may be a bit scarey for non-UK divers, I have to say I felt strangely at home.

Deeply into caves
The thrill of exploring and mapping a huge cave system in Mexico regularly takes experienced US cave-diver Kay Walten under water for more than five hours at a time

Im toting a tank across my chest to the waters edge like Im carrying a baby. For this dive my husband Gary and I will need six single tanks, our 15-litre back-mounted doubles and four scooters (diver propulsion vehicles). Its a lot of equipment, but this is going to be a long cave dive. Im already tired today after driving for an hour in Mexicos summer heat and humidity.
Three more miles on a bumpy coconut road finally brings us to our destination the path that leads to the surface pool. As we begin to unload the equipment, my mind drifts to the dive we have planned for today. Five and a half hours of bottom time sounds like a life sentence at this point rather than fun. If it werent for all the effort so far, I would just as soon turn around and head for home. But having come this far I dont want to call the dive off.
The air feels syrupy thick and hot in my lungs. The mosquitoes are buzzing my head like kamikazes. As the sweat drips from my face, I feel like I could cry, not from sadness but from exhaustion. The day-to-day frustrations of life here in Mexico are wearing me down. I feel like waving the white flag of surrender, yet theres no turning back now. Ill relax tomorrow. Now its time to don the wetsuit and head in 4000m to the end of the line.
Our project, Yaxchen, is a long chain of caves connected to a number of surface pools (cenotes). Although the cenotes are visible from the air, theyre isolated from us by a vast mangrove area that acts as a barrier to our exploration. Flowing fresh water emanating from inland has created both the cenotes and the cave. To date, weve successfully connected 20 of the cenotes through an extensive labyrinth of passages, and in the process explored more than 15,000m of cave.
This cave isnt picture perfect like the ones you see in dive magazines. The stalactites and stalagmites have been eroded away by the passing current and time. The huge cenote pools are green with algae in the summer heat. Some turn red after the rain from tannic acid. The beauty here is an acquired taste.
The surface pools, which are so numerous in this cave system, contain many unusual fish. Schools of tarpon are on top of the food chain in these neighbourhoods, with a crocodile or two making an unexpected appearance. We arent big fans of open-water diving, and with crocodiles lurking about were anxious to swim back into the darkness and security of the cave.
To go two and half miles horizontally on scuba with any degree of efficiency takes a lot of equipment and a good bit of practice. We use a system invented by cave divers called double scoot-double staging. We ride one scooter in approximately 1300m while breathing one of the two stage bottles we carry, all the while towing a second scooter.
Then we drop the scooter and tank, pick up a full tank left in the cave on an earlier dive, and pull the towed scooter around in front. With the second scooter we continue into the cave for another 1200m. Finally, we drop the second scooter and stage bottle, leaving us with one stage bottle each and our doubles to use for the upcoming swim. This system only works in Yaxchen because of its shallow depths and numerous cave openings along the route.
The swim is long, 1500m to the end of our last exploration. There we left the end of the line in an enormous cave. A cave so dark and wide that the walls can sometimes not be seen. This dive is stressful. My first scooter seems to be playing up on the way in. The thought of it not working when I get back to it eats at my brain. I try to focus to keep my breathing down. Its so far to the end of the line that each breath reduces the amount of cave we can explore once we get there.
White globs of something drift by in the water column. Both Gary and I telepathically wonder if these might be the underwater counterparts to the cave snot-tites that were described in Junes National Geographic. More finning again, endless finning. Keep pushing its like well never get there. One hundred minutes into the dive we find the end of our last exploration push. With only 500psi in our doubles remaining from our allotted penetration air, we tie off and swim westward, hoping to find the last two cenotes in our chain of caves.
Gary is leading the push, with me behind to observe the cave around us and look for leads. Within 100m the passageway ends in a room with a small vertical crack too small to pass through. Light from above illuminates the reddish water but there is no way to investigate. This crack is hardly the big surface pool wed hoped to find.
We regroup and decide to backtrack for 100m to check out the unexplored cenote I spotted on our last dive. This one has a fallen tree on top of a large debris pile that disappears into a milky yellow layer of water. We look at one another and simultaneously wonder if this might be a haven for our reptilian friends. We decide not to surface. Almost time to go, we are close to our thirds rule on air.
Frustrated, we call off the dive and head for home its 4200m to the truck, dry clothes and something to eat. There were no high fives under water, no smiles of success, only looks of defeat after coming so far. I guess every dive cant be great or you wouldnt be able to tell them apart. Three small turtles paddled around one of the surface pools. That gave me a special grin, a reminder of how interesting and special this remote area is. But it didnt elevate my mood.
The scooters are a welcome sight after all the swimming. Picking up our stages and scooter we zoom off. It is 40 minutes, or 1200m, to our next pair of scooters. With 450m to go, the yellow battery-low indicator light illuminates and my speed diminishes. I signal to Gary that my batteries are burning out. He whips out the tow clip and begins pulling the depleted scooter, and me, through the cave. Over the years, this has happened on several occasions. All batteries have their limits. Our deco time is still ticking down. As we approach the next surface pool we rise to 3m of depth. I signal to Gary to tow the scooter Ill swim the 350m to our next scooters, just keeping below the 3m decompression obligation.
Tired and worried about the batteries in my next scooter failing, I pick it up and pull the trigger for the last 1300m home. My scooter runs well. I watch and listen like a hawk for the slightest decrease in power, yet it purrs all the way to our starting point.
We surface exhausted. It was a long dive for only 100m of new cave. After a slow quiet walk to the truck to ditch our tanks we re-hydrate and eat a couple of meusli bars. An hour later we have all the equipment back in the truck except two empty tanks that are still 1300m back in the cave. Theyll have to be brought out later on another set-up dive. Its not until we are packed up and headed home that I can finally relax.
Dives like this are not a lot of fun. It isnt until weve had a meal and a good nights sleep that the impact of the dive hits home. Although it wasnt very productive, were still in awe of this enormous cave. We begin to appreciate the dive not for the new cave we have gained, but for the size and power of these tunnels of darkness.
The image of the sun illuminating large cavern zones, and of these caves that start and stop in lengthy surface pools, has been burned into our memories.
I often feel infinitesimal in this large cave, wondering why I spend my life doing this and wondering, who cares But I cant stay away. I feel entranced by this cave which has swallowed me whole. The experience of cave exploration is enriching beyond words and sometimes it takes a hard cave dive like this to make you appreciate what has been accomplished. I feel a deep respect for the cave environment and Im glad that its rewards must be earned, not given.
Why go cavern diving?
  1. The beauty - the light falling through the cavern opening creates stunning pools of blue, and the reef outside looks pinsharp and gorgeous. Youll come across beautiful and intriguing rock formations, fossils and stalactites. Where a layer of salt water meets a layer of fresh water you get an underwater surface called a halocline, which scatters the light and blurs the viz as you pass through it.
  2. Adventure - the excitement of entering the darkness of a new cavern and wondering what youll find there.
  3. Strange creatures - such as the rare and wonderful cigale (a squat lobster-like cave-dwelling crustacean), dole-eyed orange-coloured cave-dwelling fish or huge conger eels.
  4. Self-awareness - a cavern is no place for sloppy diving, so it makes you focus on all your diving skills.
  5. Intensity of experience - if youre feeling a bit dived-out, a cavern will present you with a series of new challenges and remind you why diving is truly an adventure sport. Feel that adrenalin rush!