What does Acts 27:20 mean?

Luke, Paul, and Aristarchus are on a ship. They are travelling along with the ship's owner and crew, a centurion, several soldiers, and enough passengers to add up to 276 people. They tried to make for a harbor sheltered enough to spend the winter, but shifting winds blew them into a full-force gale (Acts 27:6, 12–15, 37).

They think they're headed for the Gulf of Syrtis off the coast of Libya, but they can't see the sun or stars to give them an idea of their direction. Magnetic compasses won't be invented, by China, for another 800 years. The gulf is well-known for shallow sandbars that trap ships far from shore. If they get stuck, the waves will tear the ship apart—and everyone on board will drown in the maelstrom. The sailors have already thrown the rigging and some of the cargo overboard; there's not much else they can do (Acts 27:16–19).

Luke's account of the sea voyage alternates between the details of the journey and Paul's responses. The time is ripe for Paul to act. He told the captain and pilot not to leave Fair Havens, but when the centurion dismissed his suggestion, there was nothing else Paul could do (Acts 27:9–11). Before they left, he told them choosing to leave would probably cost them the ship, the cargo, and all the lives onboard. In the next verse, Paul steps up, gives them an "I told you so," and then gives them hope (Acts 27:21–26).

Paul has apparently been praying. An angel appears to him and says, "God has granted you all those who sail with you" (Acts 27:24). They will lose the ship and cargo, but not before the winds shift again and drive them closer to Rome. The centurion starts trusting Paul's judgment. Before they reach land, the military commander will even save Paul's life (Acts 27:30–32, 42–43).