This will clarify it
Jesus did a lot of miracles. We don't know how he did them. Jesus is God, so he can do anything. Walking on the water was not Jesus' ordinary way of getting around. He did this miracle, like other miracles, to teach his disciples and to show them his power. Jesus is Lord of the laws or the universe - he's in charge of the water, too, so he can walk on it whenever he wants to.Doesn't this just make you want to go back to Sunday school again?