What does Exodus 8:3 mean?
Pharaoh may have thought he could ignore the first plague (Exodus 7:23). His people were forced to dig for water (Exodus 7:24) because the Nile had been transformed into putrid, decomposing blood (Exodus 7:20–22). Yet the king had servants to do this for him. There may have been insignificant impact on him, personally. The second plague will affect the entire country (Exodus 8:2), including Pharaoh's own home, his own servants, and even the Pharaoh himself.Egyptian conjurers will also be able to summon frogs (Exodus 8:7), much like they were also able to mimic Moses' and Aaron's sign (Exodus 7:10–13) and the first plague (Exodus 7:20–22). But they seem unable to remove the frogs, causing Pharaoh to approach Moses and request the plague be lifted (Exodus 8:8). The Egyptian deity Heqet was a frog goddess, so the onset and ending of the plague on God's terms (Exodus 8:9–13) makes a point about the Lord's supremacy over false gods.
That the Nile "swarms with" these creatures might mean that they thrashed to escape as soon as the water became blood. Or it may mean that this plague did not happen until after the first plague's week was completed (Exodus 7:25).