We took ship. — Literally, we embarked in the ship. The article probably, though not necessarily, indicates that they went in the same ship that had brought them, and which, after discharging her cargo at Tyre, was now bound for Cæsarea.
Related Commentaries of Acts 21:6
Acts 21:6
6 And when we had taken our leave one of another, we took ship; and they returned home again.