If the audience doesn’t understand this first demonstration, Mark makes it all the more explicit when Jesus gets off the boat and encounters a bruised, howling, shackle-breaking demon possessed man (Mark 5:1-13). Jesus commands the spirits to come out of the man and permits their request to enter into a herd of pigs grazing nearby. When the unclean spirits enter the pigs, they run down the embankment and drown in the sea. Various interpretations have been proposed regarding this event; however, if the sea is associated with evil and is the home of evil spirits, then it is easy to see that Mark is portraying the spirits as going home where they belong. The man in whom they had dwelt was set free from their influence. Mark is making the same point as in the story about the storm at sea. Jesus has power to free humanity from the forces of evil which seek to oppress.
This must be a point that Mark wanted drive home because in chapter six Jesus walks on the water to reach the disciples who are struggling at the oars of the boat against an adverse wind (45-52). We should not be surprised that they think he is a ghost. After all, the sea is a place where spirits loom. But Jesus identified himself and got into the boat. When he did, the wind ceased. Once again the disciples were astounded. Not only does Jesus have the power to command the forces of chaotic evil and free human beings from oppressive forces, he is able to trample those forces underfoot as well.