I read that the province of Judea was important because of the sea route that lay on its shore - since Augustus the city of Rome became dependent on grain imports from north Africa - especially Egypt.
Was the long passage around the Italian peninsula, Aegean sea, Levant to Egypt considered to be significantly safer than the shorter one via Sicily - Carthage (or what was left of it) - North Africa ?
What do we know about Greek and Roman maritime navigation? When did they start to navigate by the stars rather than remaining exclusively near the coast line? What were the risk of maritime navigation? Do you know of any books that cover the subject of maritime navigation in classical Greek and Roman times?
You want to read Casson's Ships and Seamanship in the Ancient World and Ships and Seafaring in Ancient Times. Despite the fact that their names are almost identical and are very unimaginative those are the two most complete treatments of ancient seamanship. Despite the unfortunate stereotype that the Romans somehow had this irrational fear of everything nautical, they were quite innovative and skilled sailors--one doesn't ride the monsoon winds to India without knowing how to sail a boat. I don't know all that much about the specifics of maritime trade (so take a look at Casson), but most the grain supply from Egypt was largely entrusted to the navicularii, owners of merchant ships over a certain tonnage that the state contracted to carry the annona, the public grain supply. Romans were perfectly capable, though, of sailing in the open waters of the Mediterranean, particularly with the wide, deep-draught merchantmen which were used to carry cargo--there are countless ancient shipwrecks throughout the Mediterranean, some of merchant ships carrying cargo in excess of 250 tons, often quite far from shore. Limiting yourself to sailing along the seashore was mainly something limited to triremes and other light military vessels, which were constructed for war (particularly for speed) rather than seaworthiness--an Athenian trireme had to be beached at night and could only carry a day's supply of food and water aboard, forcing the crew to forage at the end of the day. Larger quinquiremes and other vessels would not have to be beached like this, and the coast had ceased to be the only, or even the main, method of navigation for some time. When possible sailors might sail along the coast, but the the OCD attributes this largely to the lack of real sea charts that would enable navigation by day--by night of course plotting a course by the stars or the moon (presuming it was clear) was well known in the Mediterranean world from an early date