Part of the River Cetina will reach the sea as a subterraneous river, ending its journey under the underground karst depths at Dubaci in Vrulja where the Mosor and Bikovo mountain ranges meet. In numerous diving guides this site is marked as one of the best in Europe – a cliff that drops into the sea to 100 m and waters mixing vertically with columns of fresh water rising up from underwater springs.
Diving tipsThe site can only be reached by boat and anchoring in the shallows is compulsory. Descent is 20 m from the boat towards the vertical wall and a drop to 30 m beneath which lies a freshwater source of the River Cetina. Another source, which runs dry during the summer months, lies deeper down along the wall at 55 m. The wall continues to fall to 100 m. Extreme precautions are required at the cave’s entrance zone as there is turbulence created by the mixing of salt and freshwater sources. Crawling along the seabed is the only means of entering, as swimming results in being lifted upwards to the surface by the freshwater current. The temperature is around 18 °C. Dives are almost impossible during the winter months due to strong currents.
Marine lifeUnlike other wider estuaries where contributing rivers bring sand and silt, the Cetina Estuary has a rocky seabed, but one abounding in life. Strong currents and the constant pressure of freshwater sources enable the growth of plankton and a food chain founded on filtrators. There are numerous colonies of sponges, stingers, sulphur sponges, yellow sea anemones, red Crambe sponges and sea worms. The pink jewel anemone dominates the cave’s entrance zone, while the walls inside are void of life. Sea bass and grey mullet are also found here.