Short answers, pulled from the story.
The maximum depth of the Adriatic Sea is 1,233 m, located in the South Adriatic Basin. The Northern Adriatic is the shallowest basin, rarely exceeding 100 m, and measures only 15 m deep at its northwestern end near Venice and Trieste.
The Adriatic Sea contains more than 1,300 islands and islets, the vast majority along its eastern coast. Croatia alone counts 1,246 of them, including the largest islands, Cres and Krk, each covering about 405.78 km2.
Venice floods because of a combination of tidal amplification from the Adriatic's narrow basin shape, sirocco-driven storm surges, and soil subsidence. The highest recorded flood reached 194 cm above normal on the 4th of November 1966. The MOSE project, inaugurated by Prime Minister Silvio Berlusconi in May 2003, involves 79 inflatable pontoons placed at the three entrances to the Venetian Lagoon that rise to block incoming water when tides are predicted to exceed 110 cm; the barriers were first deployed on the 3rd of October 2020.
The name Adriatic is linked to the Etruscan settlement of Adria, which most likely derives from the Illyrian word adur, meaning water or sea. In classical antiquity the sea was called Mare Adriaticum or Mare Superum, and during the early modern period the entire sea was also known as the Gulf of Venice.
Six countries have coastlines on the Adriatic Sea: Albania, Bosnia and Herzegovina, Croatia, Italy, Montenegro, and Slovenia. More than 3.5 million people live on its coasts and islands, with the largest cities being Bari, Venice, Trieste, and Split.
The Adriatic Sea collects a third of all the fresh water flowing into the Mediterranean, making it a dilution basin for that larger sea. Rivers draining into the Adriatic discharge up to 5,700 m3/s, led by the Po River at 28% of the total, and submarine springs add a further estimated 29% of the total water flux. The sea's entire volume is exchanged through the Strait of Otranto in about 3.4 years.