All year round there are scheduled ferry lines between Bar and Bari (Italy), as well as Bar and Ancona (Italy).
Montenegro Lines is the naval company that connects Montenegro to Italy with a regular service all over the year. The fleet is made of ships "Sveti Stefan I" and "Sveti Stefan II" connecting the italian ports of Bari and Ancona to the port of Bar in Montenegro.
More information on ferryboat lines, timetable and booking you can get via Montenegro Lines website.
There is also local ferry line which goes across the Kotor bay. It makes the trip from one side of the bay to another significantly faster, but do bear in mind that during the high season (mid July to mid August) there could be significant traffic jams on this line. For the additional information and price list refer to the Pomorski Soabracaj website.