There's Balkan peninsula separating Italy and Turkey (former Ottoman Empire) but the sea is called the Mediterranean.
When the Ottoman Empire controlled the Balkans, the Adriatic Sea separated the Italian states like Venice, Tuscany, the Papal States, and the Kingdom of the Two Sicilies from the Ottoman Empire.
The Tyrrhenian Sea separates the island of Sardinia from the mainland of Italy.
The Adriatic Sea :)
The only ocean that the Ottoman Empire touched was the Indian Ocean. However, the Ottoman Empire also touched the Black Sea, the Mediterranean Sea, the Red Sea, the Gulf of Aden, and the Persian Gulf.
The Tyrrhenian Sea separates the island of Sardinia from Italy.
Italy
Adriatic sea
There are several countries and a sea between Italy and Serbia.
The Smelly Sea.
The body of water off the eastern coast of Italy is the Adriatic Sea. It separates Italy from countries like Croatia, Slovenia, Montenegro, and Albania.
The Adriatic Sea separates the Italian and Balkan peninsulas.
The Ottoman Empire
Italy and [The former country of] Yugoslavia are separated by the Adriatic Sea