What was the third plague of Egypt?

The Plagues of Egypt were ten calamities that, according to the biblical Book of Exodus, God inflicted upon Egypt as a demonstration of power, after which the Pharaoh conceded to Moses' demands to let the enslaved Israelites go into the wilderness to make sacrifices. God repeatedly hardened the Pharaoh's heart to prevent him from consenting until after the tenth plague. The Israelites' eventual departure began the Exodus of the Hebrew people.