If you read the Old Testament, you get the impression that water is scary. From the very beginning (Genesis 1:1), water is portrayed as murky, mysterious, and chaotic. In Genesis 6, God uses the waters to judge the world.
Yet, in the story of the Exodus (chpt. 14), when the Red Sea appears to be the final obstacle for the Israelites on the way to their freedom from slavery, YHWH shows that He is Lord of the waters.
The children of Israel were not a particularly seafaring people in the Old Testament. They were desert people. So, by the time of Jesus, the "seas" had come to represent the source of evil itself--part of God's good creation, but a part of which they had no control.
In Daniel 7, the prophet Daniel has a vision of four beasts who emerge from the sea. They are all kinds of scary--lions, leopards, and bears (oh my!), but with wings! In fact, the scariest one had ten horns. This is the stuff nightmares are made of.
Yet, Daniel's vision ends with one "like a son of man" defeating the beast. He is able to so because "He was given authority, glory and sovereign power; all nations and peoples of every language worshiped him. His dominion is an everlasting dominion that will not pass away, and his kingdom is one that will never be destroyed."
This is what makes Jesus' miracles regarding the seas so important. Jesus is not a parlor magician, trying to do cool stuff just to get people to believe Him. All of Jesus' miracles are rooted in God's Story. In the case of our story this Sunday, Jesus walking on water (Matthew 14:22-33), Jesus shows that just as the Spirit of God hovered over the waters of creation, Jesus is the one who hovers over the waters of new creation. And the same God who parted the Red Sea to deliver his people, is present with the disciples.
What are the things that are dark and scary to you? You watching the news? Is it freaking you out? Remember: you serve the God who parts the seas, defeats the monsters, and walks on top of the chaos.