The plagues of Exodus correspond to the gods of Egypt: each plague (with the possible exception of lice) demonstrated the impotence of an Egyptian god. For example:
Nile River (Ex 7:14–25): Changed to Blood. This plague was against the god Hapi, spirit of the Nile in flood and “giver of life to all men.” The annual innundation was called “the arrival of Hapi” (57). He was especially worshipped at Gebel Silsileh and Elephantine. The Nile water was the transformed life-blood of Osiris. The fact that the Nile turned to blood, which was abominable to Egyptians, was a direct affront to one of their chief gods. Although the fish-goddess was Hatmeyt, all the fish in the Nile River died!
David Livingston’s Article, The Plagues and the Exodus, The Bible and Spade 1991 (vol. 4) sets out the plagues and the corresponding god — including the incident involving the staffs and the serpents. The purpose of the plagues thus demonstrates the absurdity of those who trust in false gods. This same pattern runs through out the OT. Thus, God brings a drought upon Israel for worshipping Baal, the storm god (1 Kings 17).
An interesting take on the plagues was quoted in the Livingston article. Personally, I found the “natural” explanations seem like a long way to go to deny the existence of God:
The first plague, blood, is the red clay swept down into the Nile from the Ethiopian highlands. The mud then choked the fish in the area inhabited by the Israelites. The fish clogged the swamps where the frogs lived; the fish, soon infected with anthrax, caused the frogs (the second plague) to leave the Nile for cool areas, taking refuge in people’s houses. But, since the frogs were already infected with the disease, they died in their new habitats. As a consequence, lice, the third plague, and flies, the fourth plague, began to multiply, feeding off the dead frogs. This gave rise to a pestilence that attacked animals, the fifth plague, because the cattle were feeding on grass which by then had also become infected. In man, the symptom of the same disease was boils, the sixth plague (pages 5-6).