In Biblical culture the sea is the symbol of chaos and anti-creation. Often it is identified with threat and death. In the story of Exodus, God’s people are saved because the sea disappears for a moment (Exodus 14:21-22). In the book of Jonah, the prophet is thrown into the sea and dwells inside the monster of the sea for three days (Jonah 1:11-12; 2:1). In Mathew’s Gospel we heard earlier that Jesus sent the pigs who have unclean spirits to the bottom of the sea: that is the place where evil spirits are supposed to dwell. When the author of the last book of the Bible, Revelations, describes the new heaven and the new earth of the latter days he says, ‘And there was no longer any sea’ (21:1). So what does it mean when we hear that Jesus is walking on the sea?
Source: Jesuits in Britain