That ship is the Church. That stormy and dark night is this present time. That turbulent sea is the world. That harbor is the appearance of our Lord Jesus Christ and the glory of His kingdom to come. That one light is the Word.
Many lights appear in the dark night beckoning the ship.
They are flashed by would-be preachers that proclaim the word of man. Hence, it is the Word that must be preached. It is the Word. Note the singular. A minister of the gospel must not be a preacher of words, not even of the words of Scripture.