Were you planning to reach Bari by ferry, you can find here a list of the main connections to the other side of the Adriatic and Ioanian seas.
As some of these lines operate on seasonal schedules, you may wish to make sure that specific connections are actually active by the date you are planning to come to Bari.
The following connections to Brindisi (ca. 80 km south to Bari) are partly operated on a seasonal basis: