The Adriatic Sea covers 138,595 square kilometers. The total length of all coastlines (mainland and islands) is 7912 km, and the indentation coefficient is 6.1. The total length of coastline (mainland and islands) in the Republic of Croatia is 5835 km, and indentation coefficient is 11, and it is one of the most indented coasts of the world. The land coastline of the Adriatic Sea is 3737 km, out of which the Croatian coastline is 1777 km. The length of the Adriatic Sea is 783 km and the width is 217 km.
In the Gulf of Trieste maximum depth is 25 m, which grows towards the south, and in the Southern basin it is 1240 m. The islands lie mainly along the Croatian coast. Out of a total of 1250 islands, islets, reefs and rocks, majority of them is in Croatia (1185). The largest islands are Krk (410 sq. km), Cres (405 sq. km) and Brac (395 sq. km). In its present form the Adriatic Sea was created in the post-Pleistocene rising of the sea levels for 96 meters.
The sea temperature grows from north towards the south. The lowest temperature of the surface layer of the sea are in February (7-13° C), and the highest are in August (from 22° C to 25° C). Open sea is warmer than the coastal areas. The Adriatic Sea is one of the saltier seas. The salinity decreases from south to north. The average salinity is 33 ‰. The transparency of the sea is the lowest in the north Adriatic (5-39 m) and the highest in the southern Adriatic (16-56 m). The air temperature is the lowest in January, with average temperatures of 10° C in the south and 2° C in the northern Adriatic, and it is the highest in July with average temperatures of 22° C - 26° C.