“And after three months we departed in a ship of Alexandria, which had wintered in the isle, whose sign was Castor and Pollux.” – Acts 28:11
What is the point of giving us the ship’s figurehead? It doesn’t further the narrative at all.
The point is: it’s an eyewitness detail. Luke gives it, because he was there (this is one of the “we passages”) and Castor and Pollux were the sign on their ship.
It’d be like me saying, “We drove to Morgantown in a car that had a “Baby on Board” sign on it. Why mention the sign? Because it was there and I included it in my eyewitness report. Maybe other passengers didn’t even see the sign, but it stuck out to me, so I included it in mine.
It is given to cement the Bible’s historicity and veracity.
A Verse A Day 