Adriatic Sea

Depths The shallowest part of our sea is in Istria, where the depth does not exceed 50 metres. From Pula, the seabed mildly drops, making a long, narrow valley which extends from Zirje towards Italy which is called Jabucka kotlina. The biggest depth there is about 240 metres. From Jabucka kotlina, the bottom rises to Palagruza reef where the biggest depth is 130 metres. Towards the south, the bottom drops steeply towards the Juznojadranska dolina, where the biggest measured depth is about 1,300 metres.

Sea currents occur under the influence of winds, the difference in pressure, temperature, and the differences in salinity. With respect to the direction, they can be horizontal or vertical. There are also bottom currents which appear as the consequence of moving of water from warmer areas to colder ones, during which the surface layer gets cold and descends towards the seabed. Currents are weakly observable in the Adriatic.The speed of currents changes in particular areas, but it also depends on time periods. The average speed of currents is about 0.5 knots, but they can also reach the speed of 4 knots.

Tides In the Adriatic, the high and low tides have relatively small amplitudes. In the southern part, the difference is rarely above some forty centimetres, while in the northern part it is somewhat bigger, so that it comes to 1 metre in Istria and the Gulf of Trieste. In some narrow channels and bays, the high tide can grow considerably during a strong sirocco. That phenomenon is characteristic for big and deep bays of the southern Adriatic. The tides are of a mixed type, which means that their rhythm is semidiurnal during the new and full moon, and of a daily type during the first and the last quarter. Their amplitudes are very irregular.

Waves in the Adriatic Waves occur primarily as the consequence of the blowing of winds. The bigger the reach, i.e. the surface across which the wind blows, the higher the waves will be. Their strength depends on the configuration and the exposure of the coast. In that way, mixing of the surface layer with water from the deep is enabled, and the interaction between the atmosphere and the sea. We distinguish the crest and the trough of a wave. The length of the wave is the distance between two troughs. Most often, heights of waves in the Adriatic are between 0.5 and 1.5 metres, and they very rarely exceed 5 metres

Nautical Radio Service and Communications Service
The whole of the Croatian coast is covered by radio communications rather well. The radio service for protection of human lives and safety of navigation is provided by Plovput from Split, through radio stations Split and Dubrovnik, which cover the southern Adriatic, and Rijeka, which covers the northern part of our sea. According to the standards of the GMDSS system (Global Maritime Distress and Safety System), the channel for automated receipt of digitalized distress calls is the channel 70, after which the communication is transferred to the operating channel of the coastal station, i.e. a harbor master's office (16 or 10). GMDSS system has been in use since 1 st February 1999, and on the present VHF channel for distress calls, the channel 16, constant listening will be possible still for some more time. For a direct call to a harbor master's office, the channel 10 is used.