The Trieste bay is a shallow bay at the northernmost part of Adriatic sea. It is confined with a virtual line between Grado in Italy and Savudrija in Croatia. It’s area is around 550 km2. Its average depth is only 16 m and the deepest parts reach 37 m. The temperatures of the sea are between 26 °C in the summer and 9 °C in the winter.
The predominant rock on the coast is flysch, which on some steep cliffs descends right into the sea. Part of the coast, mostly in bays, is of accumulation type with rivers draining into the sea. The sea floor is more or less flat and covered with a layer of thick sediment. In places, it is overgrown with communities of vascular plants, such as Poseidon Seagrass (Posidonia sp.). The sea is rich with nutrients and highly productive, while mainly smaller bays are significant spawning habitats of several commercially interesting fish species.
Major human activities in the area are: fishing, mariculture, marine cargo shipping, recreation, and scientific-research work. In some smaller areas, conservation management takes place, such as in Sečovlje Salina Nature Park, Strunjan Nature Park and Škocjanski zatok Nature Reserve