What does Acts 27:18 mean?

Winter storms on the Mediterranean are fierce. Still, it's unlikely the crew had seen anything this extreme. Paul warned them not to leave Fair Havens on the south coast of Crete. Yet, since Fair Havens's port isn't sufficient to winter in, the ship's owner and pilot decided to try to get to Phoenix, just to the west (Acts 27:9–12).

They were less than halfway to Phoenix before winds shifted, blowing them southwest, away from shelter. Near the island of Cauda, they manage to bring in the lifeboat, which was dragging behind, and use ropes to stiffen the hull (Acts 27:13–17). The winds keep driving them toward the Gulf of Syrtis, a large area filled with shallow shoals and sandbars. The wind is ferocious; the waves are fierce. They need to stay high to avoid the shoals, but not too high or they'll capsize.

The ship is an Alexandrian ship, most likely hired to bring wheat from Alexandria, Egypt, to Rome. The 1.2 million people of Rome use hundreds of thousands of tons of grain a year. It's unclear what the "cargo" is, however. They won't dump the wheat until they absolutely have no other options (Acts 27:38).