The ancients divided the navigational year on the Mediterranean into four periods (Hesiod Works and Days 663-68; Vegetius Military Institutions of the Romans 4.39; compare Genesis Rabbah 6:5b, "The crossing of the Great Sea too: Thus saith the Lord, who giveth a way in the sea [Is 43:16]—from Pentecost until the Festival [Tabernacles]"—mid-May to mid-October). Optimum sea travel could be expected during the summer months, May 15 to September 15. Dangerous times for sailing were September 16 to November 10 and March 11 to May 14. Sea travel on the Mediterranean ceased between November 11 and March 10.

As the ship lies in port at Fair Havens, it is already the dangerous period—after the Fast, the Jewish Day of Atonement, which occurred in the fall, the tenth day of Tishri. In A.D. 59 this would have been October 5 (Marshall 1980:406).

Paul's warning is well founded (v. 10). Vegetius described the dangers of "winter sailing" as scant daylight, long nights, dense cloud cover, poor visibility and the double raging of winds, showers and snows (Military Institutions of the Romans 4.39). The dangerous period saw the beginning of such conditions.

As the centurion, the ship's captain (NIV pilot) and the ship's owner or his representative confer, the majority, possibly including most of the rest of the crew, reject Paul's counsel and decide to risk a forty mile-journey out in open sea around Cape Matala to Phoenix. Fair Havens's harbor was open to the east, leaving ships unprotected against winter winds (Earle 1982). Phoenix, at the west of the promontory Cape Mouros, was better suited for a wintering ship. The present Phoinika Bay fits the description, for it has an inlet that faces southwest, and there are traces of a inlet, now marred by silting and an earthquake, that faced northwest (Finegan 1981:196). Paul's cautionary word is the first of a number of initiatives in which the apostle demonstrates that he is indeed his "brother's keeper."