The caves of the Paklenica region have been kind to us once again. This time we came to Croatia to continue the Velka Vrulja exploration (read more: Velka Vrulja almost one kilometer passages discovered!), but we had also plan for another cave – Vrulja Modric. The plan was pretty simple – just find a continuation and reach beyond 600m!
We’ve made already few dives in this cave last year and in May 2021 but the very poor visibility always stopped us around 600 meter. Each time in the same place – tricky chamber, our crux on the way inside the cave.
This time we were richer for the experiences from past dives and also full of hope for better visibility and more luck. We are coming back to Croatia. Unfortunately, after our arrival, it turned out that a group of experienced cave divers had already attempted to act in Modric, but they didn’t go beyond our crux. We did lose our hope, but only for a moment. Anyway we decided to give it a try, and … this time cave let us in. We found coveted continuation and moved forward.
Vrulja Modric – karst formations
Difficulties and challenges in Modric cave
If we were to identify the greatest difficulties, it would be definitely visibility, halocline and in general diving in mixed fresh and salty water, where it was impossible to balance and trim our equipment, especially scooters, properly. Then of course ropes – gaps or loose lines or multiple parallel lines (remnants of some would-be explorers).
The visibility between 500m and around 1000m was very poor. In few places halocline make it yet much worser. We have developed our own method of moving through the cave in such a way that each diver (not only the first one) has the comfort of diving and still act as a team.
Not everytime, not everything went our way. Movie below presents real life situation – what may happen during main line fixing. Most important is to stay calm and do what you had practiced.
Vrulja Modric plans
Since we have switched our DPVs to Seacrafts we are using also ENC 2 Navigation. We were always content with precision of distance measurement as well as general route tracking. This time we were again positively surprised by the capability of this small and powerful device. Look at these two maps below. One was created by the team exploring Vrulja Modric in 2014 and 2015. The second one on the right, is combined result of our dives with Seacraft navigation. Similarity of these two is really impressive. Distance, all the turns, angles are quite the same. That shows not only that electronic navigation is collecting very valuable and precise measurements from the dive, but also how good job the other team made 6 years ago.
We were able to dive all the existing line, check some of the side tunnels and put it all together to the map. Unfortunately all side branches we were checking were just a short parallel bypasses for the corridor with the main line.
Our dives in Modric cave
We made in total six dives in Vrulja Modric spending around 20 hours inside. On five of the dives we were fixing the broken main line and one dive was dedicated for making photos. This was really fun dive, you may see effects below. On every dive in latter part of the cave we always were using Seacraft Future as backup DPV. Please remember that we were reaching distance around 2km from the cave entrance!
The results of our dives and track from Seacraft ENC2 console put on the Google map you may see on the left.
Vrulja Modric – our dives
We prefered to use as much of old line as it was possible. There are two reasons. First one, the old line was calibrated, had knots and labels with distance. Second reason was to keep one single and continuous main line. Primary line was broken in many places and sometimes on a longer distance.
The worst section was between 600m and the T junction on 1256m. That is part of the cave with worst visibility and many places with halocline. It was huge challenge and very time-consuming work (we spent in total over 3 hours fixing only this part). You need to collect every end of broken line, uncover it from the stones, then find a cave continuation, stretch the existing line, connect to reel, so you may push forward and find opposite end of broken line. Then connect them together, stretch it back to ensure no loose line in the cave, make a final tie and cut a reel.
Of course much easier would-be just to put our own, new line, but we wanted to avoid the unnecessary danger in the form of a loose old lines or duplicating ropes just in case of any emergency returns, or coming back in low visibility. In our opinion this is additional, unnecessary risk, especially in poor visibility, we definitely wanted to avoid.
Vrulja Modric is also known as Black Cave. The second name suits the entry parts of the cave quite well. After first T intersection the character of the cave changes drastically (especially in the right corridor). The walls become bright and reflect light beautifully. Also the visibility changes for much, much better.
Movie below present short summary of our dives in Modric and reaching 3 out of 4 known end of lines. Due to narrower section and few restrictions at the end of left branch we reached only almost the end of line (according to the available map) leaving last 50m as a good motivation to come back to this cave in future.