“Kamene Tajne” alias “Stone secret” is the name of the expedition made last August to the Kusa spring (Croatia) organized by the DDISKF: the Croatian speleological group with which I have collaborated for many years.
The main objective of my group of cave divers was this Spring that flows near the mouth of the Zermanja river, southwest of the Velebit chain.


In August 2017 explorations had reached 1,700 metres and passed through three siphons and a series of air-filled sections. This year, between July and August, we returned to this system of underground cavities that are connected to each other and accessible from the outside (karstic system). Ten days were taken up mapping the part already explored in 2017, and seven more days were used to continue the explorations and to map the new galleries. The final result was a total of 2,200 meters of cave topography consisting of 2,700 meters of explored cave which includes 1,350 meters of flooded tunnels.


The complexity of the exploration arises from the need to pass through the various siphons which, due to their depth and length, require equipment that is heavy and bulky out of the water. This means great effort is needed to pass through the air-filled sections as you have to get out of the water in your drysuit and carry equipment that can weigh up to 35 kilograms on your back. These efforts are made even more difficult due to the rough and slippery ground and having to climb and squueze through narrow passages. In addition to the tiring part of the route through the air-filled sections there are the number of difficult repetitive dives required to cross the flooded sections. This situation exposes you to the risk of decompression sickness that could further complicate the management of the exploration.


The development and the depth of the siphons to reach the farthest part of the cave are:
first siphon: developing over 200 meters and 48 metres deep;
second siphon: developing over 500 metres and 53 metres deep;
third siphon: developing over 120 metres and 12 metres deep;
fourth siphon: developing over 530 metres and 63 metres deep.



The climbs between the various siphons were brilliantly overcome by free climbing vertical passages, over 10 meters high, which were then equipped with fixed ropes to optimize speed and safety.


There is still a lot of the Kusa Spring to be explored and the prospects are very promising. The effort required of the exploration is considerable (and not for everyone!) but the enthusiasm and the satisfaction that my group and I feel every time always urges us to return again!


Participants: Luigi Casati, DDISKF, Adriano Ballarin, Alessandro Giobbi, Carlo Venezia, Davide Corengia, Michael Walz, Patrick Deriaz, Stephane Girardin.

Thanks go to: PSS Worldwide, Diving Tecnical Center - Cylinders, Nardi - Compressors, Easydive – housings, Parisi - Suits, Suex - Scooters, Tecnodive - Booster, Utengas, Xdive - Illuminator, #PSSPeople.