John Gill Commentary Acts 28:11

"And after three months we set sail in a ship of Alexandria which had wintered in the island, whose sign was The Twin Brothers." — Acts 28:11 (ASV)

And after three months we departed
From Melita; here they stayed the three winter months, which were unseasonable for navigation; but now the spring coming on, and the weather agreeable, they left the island, and sailed

in a ship of Alexandria; (See Gill on Acts 27:6);

which had wintered in the isle ;
perhaps all the said three months, for the same reason:

whose sign was Castor and Pollux ;
or Dioscuri, that is, the sons of Jupiter; for Castor and Pollux were his sons, by Leda:

these are placed among the constellations in the Zodiac, and go by the name of Gemini, or the twins; and these were supposed to have a power of saving men in danger at sea: therefore such as were about to go to sea, first paid their devoirs, and made vows to them; which they performed when they returned, and were delivered from shipwreck; and when they were in danger at sea, they used to pray unto them:

the fiery exhalations that sometimes appear at sea, they took for them; and when only one appeared, it was looked on as a bad omen; but when both, it was reckoned to portend a prosperous voyage; hence they were considered as sea deities; and the Ethiopic version accordingly renders it here "Dioscoura", and adds, "who is the god of the mariners":

now the images of these two brothers were sometimes set at the head, or forepart of the ship, as they were in this, from where the ship took its name; as it is very common for the names of ships to be the same with the pictures or images that are placed at the head of them:

whether the centurion chose this ship because of its sign, imagining there might be more safety in it, he having suffered shipwreck already; or whether this was the only one in the island, that was going for Italy, is not certain, nor very material: the Arabic version takes the word rendered Castor and Pollux, to be the name of a man, who was the owner of the ship; for it reads the words thus, "in a ship of Alexandria", that belonged "to a man of Alexandria, called Dioscorides".