Editorial by Luigi (Gigi) Casati
Going to Croatia has been a regular occurrence over the last few years. Over time, the growing friendship with Tihi and the DDISKF members have allowed us to optimize the organization of our explorations in this amazing country.

On July 21st, the Zrmanjin Zov expeditions (Zrmanja is the name of a canyon, Zov means “view”) is officially launched with a short speech from the organizer Tihi, the notes of the Croatian national anthem, and a nice party that everybody enjoys, including the cave divers and representatives from the local authority.

The first target of the expedition is a spring that is new to us, although it was explored some years ago by a Frenchman up to the depth of -50 meters. On the morning of July 22nd, we leave the base camp in Obrovac and head in the direction of Donja Suvaja, about an hour’s drive distant. The journey offers some fascinating landscapes, as does all of Croatia.

Upon arrival, we set up the forward camp on a local trout breeder’s property. We take the equipment down from the cars, and prepare everything for a first scouting dive. The equipment is arranged into speleological bags, and is carried by ten speleologists to the Vrelo Une spring, a fifteen’s minute’s walk which first climbs sharply then heads down to the lake. While walking, I am able to catch a glimpse of the small lake in between the thick wood. The dark blue of the water creates a strong contrast with the vivid green of the trees, and I feel the adrenaline rising inside me. I can’t wait to explore that cave!

Around the small lake, the mountain wall rises vertically for more than 100 meters against the clear blue sky. The lake is about 50 meters wide and 20 meters long, the water temperature is 9 degrees Celsius and, at first sight, visibility doesn’t look too bad. Once we finish installing the regulators on the safety tanks that we will put into the water for possible emergency situations (such as technical problems with our rebreathers), the long awaited operation of putting on the dry suit and the rest of the equipment finally comes.

Alen and I go in first in order to position the tanks along the way. To begin, I take care of positioning the safety rope and tanks for the deep dive; Alen follows me and sets a 10-liter oxygen tank at -6 meters, a 15-liter 50/20 nitrox tank at -21 meters, and a 15-liter 36/36 nitrox tank at -36 meters depth. Our team member, Alan, gets into the water with his camcorder to take some shots of the cave preparation, and swims around me with his video camera taking advantage of all the times I need to stop to fasten the rope or to prepare the knots to secure the tanks. I set one last 15-liter 25/60 tank at -50 meters, and I keep going from there toward the unexplored areas. The cave has a very vertical development, many tree trunks create fascinating and mysterious shapes and shadows, and the wall appears incredibly eroded. Everything makes me believe that a long time ago this spring was a swallowing pit.
I reach -70 meters and place a 20-liter 20/70 tank. Alan stops here while I let myself fall into the abyss. I can’t see the entire tunnel, nor can I guess at its size, so I just follow one of its walls. The visibility is approximately six meters, due to the relative darkness of the wall’s rock. I soon find myself at -90 meters, where I leave the last 20-liter 15/75 relay tank, keeping one 20-liter extra tank and one 7-liter tank for my rebreather. But I am not yet satisfied, and so I let myself sink down to -103 meters, a distance of 140 meters from the cave’s entrance, and there I finally make the decision to stop the exploration…leaving the reel hung up in the void.

After twenty minutes, as I start to go up, I look around to try and understand how big that hole in the rock is; more or less, it should be 20-30 meters by 5-10 meters. I surface in just under an hour, thrilled by the experience and with one single thought in my mind: reset the equipment for tomorrow!

The following morning, after the arrival of Jean Jacques Bolanz, my partner of so many adventures, we go to the spring where I want to immediately continue the exploration. A number of problems occur that delay my start. First there is a problem to a sensor, which is quickly solved by borrowing one from Jean Jacques. Next, I realize that the HID lights don’t work because they had flooded the day before. Then – dulcis in fundo – I am missing the connection between the condom and the P-valve of my dry suit.
Therefore, since I can’t do anything else, I go down to secure the safety tanks on a 7mm rope at -90 meters. I am not comfortable with the idea of leaving them hanging in the void on a tiny 2mm exploration rope.

On July 24th, I take the day to rest while Jean Jacques prepares to begin the topography. I propose that Jean Jacques choose between doing the topography and continuing with the exploration. Immediately, and with the enthusiasm of a teenager despite his 67 years, he replies that he is definitely for the exploration. With Alen and Alessandro, we take all the material to the spring where Alen will assist Jean Jacques during the decompression, while Alessandro drives into the cave to familiarize himself with it.

Photo: JJ Bolanz congratulates Gigi after he surfaces from the 205 meter/673 feet exploration dive.
With his usual calm, Jean Jacques gets ready and soon disappears beneath the surface. After 160 minutes, he resurfaces with the happiest look in his eyes and tells me that he reached -123 meters, at the very bottom of the pit, and that his main helmet lights went off. Soon after, we notice that his canister had flooded, too. At dinner, Jean Jacques describes the dive in detail. Listening to him, I start thinking that after a certain point the cave changes direction and probably heads up towards the surface.

On July 25th, it’s again my turn to continue the exploration. After a good breakfast, we get to Vrelo Une where all our gear and equipment are already set for the dive. In addition to the rebreather and its 7-liter 5/85 tank, I take two 20-liter safety tanks with two different gas blends, one with 12/80 and the other with 8/85. Once under the surface, I go down quickly, reaching -70 meters in three minutes and -123 meters in five minutes; the reel waits on a rock at the beginning of a creek that keeps going down. The night before, we had talked about going beyond that point….

I smile, and start going down. I finally reach a tree trunk to which I secure the rope before going further. Another tree trunk with a diameter of 70 centimeters lies crossways in the creek; a glance to the depth gauge shows I am at -150 meters. I feel all right, so I decide to continue the descent, observing in detail the surrounding morphology. At the depth of -163 meters, 230 meters away from the cave entrance, I leave the reel at the base of an enormous rock. It’s taken me only ten minutes to get there. Taking a look around, I can see side walls of hard rock, below and in front is the most absolute void. Where I leave the reel there are many rocks of various sizes; the steep slope is a clear warning to not touch anything with the fins.

I start to go back up. At -120 meters, I take a quick tour around what seems to be a large cave with the bottom covered by an impressive composition of tree trunks and branches; but I stay only briefly, as I don’t want to waste time and accumulate decompression minutes.

Exactly one hour after my departure from the surface, Alessandro reaches me with a new battery for my electric jacket and a flask of fresh water with minerals. Alen comes to see me at the second hour and, given that everything is going well, he decides to stay with me till the end of the decompression time. I get back to the surface after 147 minutes of dive, and I find thirty people interested in our adventure and ready to congratulate me for the achievement.

On July 26th, Jean Jacques and Alessandro start to draw the topography of the cave beginning from the depth of -58 meters up to entrance. Alen explores some small tunnels at a few meters of depth.

On July 27th, they continue the topography to the depth of -107 meters, and check out other secondary tunnels and caves, which don’t lead to any relevant exploration.

On July 28th, after two endless days spent watching the other guys diving, I am finally ready for a new exploration attempt. We get to the lake later than usual, it’s almost noon. I had prepared everything the day before, so the only things I have to do are to perform a final check of the analyzers’ calibration and to put on the gear and equipment. Once in the water, I go down to -6 meters to check the sensors. A quick return to the surface to say that everything all right, a greeting to everyone, then I swim across the lake looking for the exact point where the vertical hole is more direct and free.
Photo: Explorer, Gigi showing the profile of the dive on his computer during decompression
Just before going down, I empty completely the counter-lungs of my rebreather to exhale all the oxygen; I open the dry suit’s valve, and I start my fast descent. I get to the depth of -40 meters in one minute, then I need to use the fins to push myself deeper to -70 meters; from there, I am able to go down vertically to -123 meters. During this last trunk, I keep the PpO2 at

0.6 to avoid generating too much oxygen in the gas blend, which would force me to perform a cleaning cycle of the rebreather. Past that point, I set the PpO2 to 1 and continue to go down quickly. I use a diluting mix 3/90, and by doing so I am able to keep the PpO2 easily under control; even if, at times, I have to close the oxygen flow. I stay a few meters distance from the rope in order to better observe the hole, and to use the fins without worries. In eight minutes, I reach the reel that I left at -163 meters.

I feel so strongly the attractiveness of the unknown that it is like a loud scream inside me, but I keep it under control. I pick up the reel and unlock it while I look at the slope that continues below me. I kick myself down by pushing the fins on the floor to gain some speed, but this turns out to be a very bad move as the pressure on the rock generates an immediate landslide. In front of me there is a huge rock and fearing it can fall on me, I move horizontally to the side for a few meters in the creek while holding the reel strongly in my hand. The clay lifted by the landslide is swallowed from the bottom of the cave, and I decide to stand there and wait, suspended in the void, still. After three long minutes, when the anger of the rocks seems to cool down, I hear three nerve-wracking thuds — as if huge rocks had landed violently on a floor far below.

I go a little further down, but at -175 meters, I must stop. Below me there is a very thick cloud of clay that is impossible to penetrate. So I lock the reel and leave it hanging in the middle of the creek. I realize then that one of my three analyzers has mysteriously turned off.

When I begin my ascent I have been in the water for only thirteen minutes. I have plenty of time during the decompression to reflect on my mistake. It’s very well known that being in a hurry can lead to irrational behavior and increase the possibility of making mistakes. I also have plenty of time to record on a small whiteboard the exact depth where the tree trunks lie, and other interesting things about the environment in the cave. At the depth of -120 meters, my analyzer “magically” turns on again. The two assistant cave divers, Alen and Alessandro, are punctual and efficient as usual throughout the entire decompression time. I get back to the surface after 186 minutes.

On July 29th, Jean Jacques prepares for the exploration of the big cave at -120 meters, but at the lake we are disappointed to learn that visibility is down to about 50 centimeters. During the last few days little water has flown through and the weather conditions have been stable, so the only plausible explanation of this major change in the water conditions is that the cloud of clay I lifted had drifted up to the surface, brought by the current overnight. We spend the day fixing the equipment damaged during the past few dives. We identify and solve the problems with the battery packs; I replace the battery of the analyzer; I check some of the regulators; and we spend the remainder of the day reading and writing the expedition report.

On July 31st, we can see the safety tank at -6 meters, so hope for good conditions underwater. The sky is cloudy and the air temperature is 10 degrees Celsius, perfect conditions to wear the heavy undersuit without sweating. While getting ready, I mentally go through the key reference points of the cave and the key operations to perform so that I can anticipate every single movement of my body. I will go down as fast as I can, and this time I don’t want to make any mistakes.

In four minutes, I reach -123 meters. I know that I need to control the power in my legs to avoid an increase in breathing frequency. Visibility here is about four meters, very different from the previous days. I keep going down to -163 meters and maintain, this time, a good distance from the bottom. I get to the vertical point where I had left the reel. I hold it in my hand while the thin layer of mud that was covering it flows around me like a cloud. The walls, too, are covered by at least half a centimeter of clay that could easily mix up in the water at the slightest touch or water pressure.

At the depth of -180, I find another tree trunk. How unbelievable it is to find one down there, given that the creek is not fully vertical from the surface. Continuing my descent, at -190 meters I can see the bottom: a steep slope of gravel below me. I go further down moving on a diagonal to gain depth with the least effort possible. One of the analyzers turns off, but this time I have four on me to feel safer. I go down a few extra meters to search for a secure anchor point for the rope. My hands shake, HPNS or fear, I don’t know. But my mind is vivid clear. I decide to take the shears out of the elastic band, cut the rope, make the knot, secure the reel, use again the shears and, finally, to go up a bit. I then look at the depth gauge: in twelve minutes, I have reached the depth of -205 meters at a distance of 290 meters from the surface.

The little clouds of clay I go through during my ascent create a surrealistic atmosphere. I can’t avoid thinking of the three strong thuds I heard during my last dive. This can’t be the point where the big rocks landed because, with the steep slope and the gravel on the bottom, the noise should have been softer. Who knows what’s below that…?

I do a first stop of one minute at -160 meters exactly above the big rock. Taking a close look, I notice that it is a conglomerate of rocks. A de-pigmented shellfish with long antennas, which for sure has no problems with HPNS nor with decompression, comes to make me a kind visit. At -123 meters, I pick up the 20-liter tank that I had left for a possible emergency. After 25 minutes, at -117 meters, I reach Lorenzo who is with us to make photographs starting from the deep area at
-120 meters; an extra deep stop to capture a few images, and then we go slowly up together filming the most interesting spots.

On my way up, I also pick up the other two 20-liter tanks at -90 meters and -70 meters as well as the rope to which they were secured. In recovering the rope, I believe I generated fatigue to the forearms and, consequently, as soon as I get around -40 meters I start feeling some pain. I slow the ascent a bit in order to address the problem while remaining as deep as possible. I manage to stay at -21 meters for thirty minutes at a PpO2 of 1.6. Suddenly, the pain vanishes. I get rid of the five 20-liter tanks; I drink and eat some watermelon slices. I have all I need for a relaxing decompression.

After 295 minutes, I get to the surface happy and satisfied: the explorative dives are over. We take most of the equipment to the cars, leaving at the cave only the minimum set necessary to complete the drawing and to recover the gears.

I already dream of the day next year when I will be back in Vrelo Une to try to continue the deep dive exploration, and to see how wide that attractive wall creek really is. And, who knows, to maybe find the place where those rocks landed….

Participants: Alan Kovacevic (preliminary dive to -55 and video), Alen Milosevic, Alessandro Fantini, JJ Bolanz (topography), Lorenzo Del Veneziano (photos), Luigi Casati and, above all, Tihomir Kovacevic and the DDISKF, his speleoclub.

Right: Photo: Explorer Gigi in decompression near a big stone trapped in the root of a fallen tree.
Below: Left to right: Tihomir Kovacevic, Lorenzo del Veneziano,
Luigi Casati, and Jean Jacques Bolanz.