They came to the other side of the sea, into the country of the Gerasenes. When He got out of the boat, immediately a man from the tombs with an unclean spirit met Him, and he had his dwelling among the tombs. And no one was able to bind him anymore, even with a chain; because he had often been bound with shackles and chains, and the chains had been torn apart by him and the shackles broken in pieces, and no one was strong enough to subdue him. Constantly, night and day, he was screaming among the tombs and in the mountains, and gashing himself with stones. Seeing Jesus from a distance, he ran up and bowed down before Him; and shouting with a loud voice, he said, "What business do we have with each other, Jesus, Son of the Most High God? I implore You by God, do not torment me!"* 
Think about these words from the Word of God.
The disciples have had a very rough night on the Sea of Galilee. They experienced a terrible storm where they felt like they were going to die. They learned that Jesus has power even over the violence of nature. Jesus calmed the storm. The minute they reach shore they experience the violence of a man filled with unclean spirits. Does Jesus have power over this storm too? The looks of this man alone must have frightened the disciples. But Jesus remained calm as the violent man rushed up to Him. The unclean spirits have found a home in this poor man's body they even use this man's mouth to speak to Jesus. An unclean spirit is a demon. Demons are fallen angels who have followed Satan in disobedience to God. They know as Satan does who Jesus is. Jesus is the Son of the Most High God. They also recognize that Jesus has power over them. Another storm is about to be calmed. How horrible it must be to be filled with unclean spirits. How wonderful it is to be filled with the Spirit of God. If you have not experienced being filled with God's Spirit read the good news!
Mark 5:1-7 (NASB)