The Adriatic Sea ( /ˌeɪdriˈætɨk/) is a body of water separating the Apennine Peninsula from the Balkan peninsula and the Apennine Mountains from the Dinaric Alps and adjacent ranges. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) to the northwest and the Po Valley. Its coasts are part of (in decreasing order of coastline length without islands) Croatia, Italy, Albania, Montenegro, Slovenia and Bosnia–Herzegovina. The Adriatic contains over 1300 islands, mostly located along its eastern coast. It is divided into three basins—the northern being the shallowest and the southern being the deepest, with a maximum depth of 1,233 metres (4,045 ft). The Otranto Sill, a decrease in depth, is located at the border between the Adriatic and Ionian Seas. The prevailing currents flow counterclockwise from the Strait of Otranto, along the eastern coast and back to the strait along the western (Italian) coast. Tidal movements in the Adriatic are slight, although larger amplitudes are known to occur occasionally. The Adriatic's salinity is lower than the Mediterranean's because the former collects a third of the fresh water flowing into the latter, acting as a dilution basin. The surface water temperatures generally range from 24 °C (75 °F) in summer to 12 °C (54 °F) in winter, significantly moderating the Adriatic Basin's climate.