What does Acts 27:7 mean?
Luke is describing the sea voyage from Caesarea Maritima to Rome. Paul is going there, as a prisoner, to have his case tried before Caesar (Acts 25:6–12). Aristarchus is also a prisoner (Colossians 4:10). Luke is likely finishing his fact-finding tour for his second letter to Theophilus (Luke 1:1–4; Acts 1:1–2).The ship which sailed from Caesarea to Myra, on the southern coast of modern-day Asia Minor, was too small for open water. Paul's traveling group has found an Alexandrian ship, likely a large grain ship, capable of handling the Mediterranean (Acts 27:6). The winds are from the northwest, and they manage to sail into them by weaving through the islands. One such island, Cnidus, would be a good port to spend the winter. It's not clear if the winds don't allow them to land or if they're trying to go on to Corinth. If they can cross the southern Aegean to Corinth, they can drag the ship across the isthmus connecting Achaia to the Greek mainland. After this, they might continue past the mountains of southern Greece before heading straight west to Italy. The winds don't allow them to travel any farther west than Cnidus, however, and they turn southwest to Crete.
Salmone is on the northeast corner of Crete. "Sailed under" is from the Greek root word hypopleō. It means to sail close to the leeward side of something to get protection from the wind. When the winds are from the north, the lee side of Crete is the south where the mountain range provides smoother sailing along the southern coast. The ship only gets halfway down the coast, to Fair Havens, before they realize they're stuck. Winter is coming. Fair Havens' port can't protect ships during winter storms, and to risk the open water is dangerous. Against Paul's warning, the ship's owner and pilot decide to continue west to the port of Phoenix. The winds change, however, and come from the northeast. The ship is blown toward Libya, forcing the crew to fight a storm that seems intent on running them aground on an underwater reef. This process is depicted in the remainder of the chapter.