The Strait of Otranto is today the generally accepted dividing line between the Adriatic Sea and its neighbor to the south, the Ionian, but discovering exactly where the strait stops and starts, like many a water boundary, depends on who you ask and when. This southern boundary, moreover, is relatively recent. In a certain sense the fuzziness of its southern confines is understandable when one considers the Adriatic in a historical context that might come as a surprise to the inhabitants of, say, Scandinavia: it was long considered a northern sea. This quality in fact was what first-century Romans thought most noteworthy when they occasionally named it the Mare Superum or “Upper Sea” instead of any of its other names. “Adriatic” in turn appears to have derived from an old Etruscan city, Atria, which was located in the far north near the mouth of the Po River.
Tracing the Ancient references makes it clear that the boundaries of this sea, while obvious where the land met the water in the north, tended to be quite variable and sometimes contentious to the south, extending with Roman colonial expansion first to the Gargano Peninsula and then onward to Otranto, Roman Hydruntum. As Rome’s colonial expansion did not stop there, however, but kept growing, so too did the sea’s supposed dominion, infiltrating the Gulf of Taranto and overtaking both the Sicilian and Ionian Seas. For Procopius of Caesarea, writing in the sixth century, the Adriatic’s southern reaches appear to have extended far into the wider Mediterranean while the sea’s defining geographical trait mentioned in his History of the Wars is not a north-south boundary but an east-west one, with the island of Malta as the defining line between what he calls the Adriatic Sea, which appears to encompass the central Mediterranean, and what he calls the Tuscan, which reaches around the Italian Peninsula up to Tuscany. [I am considering adding a roughly sketched map here]
It is in this context that the geography of the disciple Paul’s experience recounted in the New Testament Acts of the Apostles 27:39 to 28:11 has often been explained: upon leaving Crete, the vessel in which he traveled was said to have encountered a storm on the Adriatic that drove it towards the Maltese coast. But here ancient conceptions of time and space have tended to confound as often as clarify. The Biblical account does not say how long they had sailed before they met the storm, only how long it drove the ship to and fro after they met it (fourteen days). If they had hugged the coast, as ancient navigators were wont to do, perhaps it skirted up and around rather than headed out to open waters, making landfall, after this storm, not on Malta, as is believed by some, but on Mljet, off the coast of Dalmatia, as others have claimed. The ancient coast lines were likely quite different than what we see today, and there is evidence to suggest that much of what is land in modern memory was then water. It turns out, moreover, that the two islands are referenced in both Greek and Roman sources by the same name—Melita—and each island has a harbor named after St. Paul, along with local attestations to his stay there after a storm and a shipwreck. Both regional and international scholarly opinion has come to the aid of such claims over the centuries, swaying this way and that with the region’s geo-political tempests. And so when the Spaniards controlled Malta, English opinion placed the great saint’s landing on Mljet, but when England controlled Malta, new research proved he had landed on Malta after all.
 Book III, Chapter 14 (https://en.wikisource.org/wiki/History_of_the_Wars/Book_III#XIV)
 See Wilkes, The Illyrians, 1992, on the ancient coast and changes since.
 Ignjat Durdevic’s 1730 Venetian monograph places St. Paul’s shipwreck on Mljet. Ignjat Đurđević: Sveti Pavao apostol brodlomac (St Paul the Apostle Castaway), Miho Demović (ed.), Dubrovačke knjižnice, 2008.