The Adriatic is about 1,000 km long and on average less than 200 km wide. It has a particular counter-clockwise current circulation. Warmer saltier waters enter through the straight of Otranto and go up the Albanian and the Ex-Yugoslavian coasts to Triest. They then go down again along the Italian coast where they join with the great input of river waters in the area between the Isonzo and the Po. A broad current system is thus formed. This system is particularly influenced by the following: the tides, the Bora wind (from the north-east) and the Scirocco wind (from the south), and by the waves these winds cause.

The drainage basin of the Adriatic Sea involves different nations, but more than 70% of the pollutant loads transported by the rivers comes from northern Italy. The area of the Upper Adriatic has less than 10% of the water volume of the whole of the sea basin.

Some of the data on the Adriatic system

• drainage basin : 220.000 square km
• sea basin : 136.000 square km
• total ecosystem : 365.000 square km
• average annual volume of the rivers : 3.900 cubic m/sec
• inflow of fresh water (yearly average includes the rainfall within the basin) : 5.140 cubic m/sec
• population of the drainage basin : 33.8 million inhab.
• population density of the hinterland : 154 inhab./square kmq

The seabed slopes downward towards the south, with minimal steepness, until East of Ancona, where the depth rapidly increases, dropping from 100 m to 265 m. It then goes up again, thus forming a trench. The sea bed goes down once again off the coast of Bari to reach a depth of 1,100 m, it goes back up at Brindisi, and then subsequently goes down to 4,000 m in the Ionian Sea.

The small areas of rocky outcrops called "Tegnue" by the fishermen from Chioggia are a very important element of the Upper Adriatic marine environment. These rocks have a triple function: they are natural reproduction areas for many fish species; they enrich biodiversity; they are a natural defence against fish trawling in the Upper Adriatic, where this type of fishing has caused great damage.