What does Acts 27:15 mean?

Paul, Luke, and Aristarchus are on a runaway ship. Paul and Aristarchus are on their way to Rome to face charges in Caesar's court; Luke is accompanying them (Acts 25:11; 27:1; Colossians 4:10). They're on a ship, likely exporting grain, with 273 other crew members and passengers, including a centurion and several soldiers (Acts 27:6, 37).

The ship had been moored at Fair Havens on the southern coast of Crete. Winter is coming, and no one wants to risk the fierce Mediterranean storms in open water. The ship's owner and pilot want to go farther west to Phoenix. Paul knows better. He warns them: even though Fair Havens is not suitable to wait out the storms, if they leave they'll lose everything. The centurion trusts the owner, and they weigh anchor (Acts 27:8–12).

At first the winds are favorable and they're able to sail straight for Phoenix. As soon as they pass the protective shelter of the mountain ranges, however, the wind shifts from the south to the northeast. The sailors try to turn the ship to face the wind, but they're too late. They put the wind at their backs and let it drive them along (Acts 27:13–14).

In the next few days, they'll reinforce the hull, throw out the tackle and some of the cargo, and lose all hope. Paul will pray. He warned the owner that if they left Fair Havens they'll lose the ship, the cargo, and their lives. Now, he apparently prays that the Holy Spirit will at least save the men. The storm tosses the south—where they just miss the sandbars off the coast of Libya—and then northwest—where they wreck of Malta. The ship and cargo are taken by the sea, but every person survives.