The Nile River was a factor in the Egyptians' lives that they depended on
(Rashi) the Nile was the main source of water for the Egyptains, since there is no rain that fell in Egypt and since they looked at the Nile as such a powerful aspect in their lives, they worshipped it as one of their gods
Throughout their days, they went multiple times to get water since this was their only source. Egypt is very dry, so without the water, they would not have been able to survive. The Egyptians worshiped the Nile as well and would pray to it
Hashem sees the Jews being put to work tirelessly by Paroah and the Egyptians
In order to try and save Bnei Yisroel, Hashem took the thing most important to the Egyptians and asked Aharon to smack the water, in order to turn it into blood
(etzion.org)Hashem chose to turn the water into blood as opposed to anything else for many reasons. One of them being: - Pharaoh made a decree to kill all the males by throwing the boys into the Nile River . - Maybe, by striking the Nile with blood, it served as a reminder to the Egyptians because they tried to throw all the males into the Nile River. Hashem showed them that blood filled the depths of their precious Nile because of their evil crime to kill the Jews. - Therefore, this shows Hashem’s power that He wanted to pursue justice unlike the Egyptian gods who did not care about morality. - Hashem struck the Nile with blood because the Egyptians tried to kill the males by throwing them into the Nile to shed their blood.
No more water. Not for the babies, not for the animals...
(Maharal) Next Slide-->
(Maharal) The Mahara states that when Hashem brought the Makkot on the Egyptians, he struck them using all the portions of the world. There are ten divisions of the world which correspond to the ten sayings with which Hashem created the world. Each makkah is in opposition to a saying that was used by Hashem to create the world. One can find in the final saying in ’בראשית פרק א which stated, “הִנֵּה֩ נָתַ֨תִּי לָכֶ֜ם אֶת־כָּל־עֵ֣שֶׂב זֹרֵ֣עַ זֶ֗רַע אֲשֶׁר֙ עַל־פְּנֵ֣י כָל־הָאָ֔רֶץ”. This pasuk states, “Hashem said behold I have given to you all herbage yielding seed that is on the surface of the entire Earth.” This is the last saying in the creation of the world that Hashem gave to the living beings for sustenance by the food that they would eat which would then return to their blood, and then the blood would sustain them and give them life. Hashem changed this saying and made the whole river blood, and thereby did an act that was the equivalent of never having created blood in the creation of the world. It was considered a loss and destruction because the addition of blood into the whole river was the equivalent of the loss of blood for sustenance. We can see from this that Hashem’s power is clear in this makkah because He created the world in a way that blood is used for sustenance, but too much or too little blood, and blood in the wrong places can be used to lead to death and destruction.
More importantly, Hashem used his power to destroy what they believed to be their god, which they are no longer able to worship.
(Oar Hachaim) The fact that the fish died was a sign to the Egyptians that this was not something brought from witchcraft or demons. If the blood would have been the result of magic or witchcraft, it would only change the appearance of the water without changing the properties of the water. The fact that the fish died showed that it was an act of Hashem and that the water took on the properties of blood that killed those who drank it including the fish. This shows Hashem’s power that he was able to change the nature of the water to become like real blood.