In the first plague in Egypt, God changed the water of the Nile to blood. What is the significance of this plague? From Exodus 7 this article explains that this plague points to God’s judgement. 

This article is an introduction to the ten plagues God brought over Egypt. The author looks at the unfolding of Genesis 3:15 (the enmity between the seed of the serpent and the seed of the woman) in the ten plagues of Exodus 7-11.