God uses water to preserve His people. God saved Noah and his family by the flood. God saved the Israelites by leading them by a mighty hand and an outstretched arm through the midst of the Red Sea. God healed Naaman from leprosy by having him wash seven times in the Jordan river. Leprosy was a picture in the Old Testament of spiritual death.
Baptism pictures the washing away of our sin.
Christ is the living water. God speaks that the child of God grows spiritually when he hears and studies the word of God, just as a plant grows which is watered. Scripture also speaks of water in terms of God's judgment upon the world. God destroyed the world with the Flood. God destroyed obstinate Pharaoh and all his host in the Red Sea.