What does Acts 27:16 mean?

An Alexandrian ship, likely exporting grain, is on its way to Rome, carrying Paul, Luke, and Aristarchus. But after making it to Fair Havens on the southern shore of Crete, the crew realized they needed to find a place to stay for the winter. Fair Havens isn't suitable. The ship's owner and pilot decided to try for Phoenix, about 40 miles, or 64 kilometers, to the west. Paul warned them it was a bad idea. They left Fair Havens, sailed west, rounded a point, and headed straight for Phoenix. As soon as the terrain turned flat, however, the winds changed. A "tempestuous" nor'easter caught them (Acts 27:14) and drove them southwest toward Cauda.

Cauda is a small island south of Phoenix; today it's called Gavdos. The hills aren't nearly as high as on Crete, but it protects the ship just enough to allow the crew to prepare for what is to come. The "ship's boat" is a skiff used to take passengers to shore if there's no deep port. It's usually tied behind the ship and dragged along, but by this time the wind and waves probably either capsized it or filled it with water.

Once the skiff is secured, the sailors reinforce the ship by stringing ropes under the hull. They quickly realize they're headed for the Syrtis: a gulf near Libya well known for hidden shoals. These shallow sandbars can strand a ship far from the shore. The shallower the ship sits in the water, the more likely they'll clear the shoals. To lighten the ship and raise the keel, the crew throws some cargo into the sea. To try to slow down, they lower the sails to the deck and toss some of the ship's tackle overboard, probably to act as a sea anchor. Despite their precautions, the crew knows it's not going to be enough and abandon hope of surviving (Acts 27:17–20).