22 And the magicians of Egypt did so with their enchantments: and Pharaoh’s heart was hardened, neither did he hearken unto them; as the Lord had said. 23 And Pharaoh turned and went into his house, neither did he set his heart to this also. 24 And all the Egyptians digged round about the river for water to drink; for they could not drink of the water of the river. 25 And seven days were fulfilled, after that the Lord had smitten the river.
The turning of the rod into the snakes had been a show of power and superiority from God, but turning the river into blood was truly a throwing down of the gauntlet, a challenge that actively hurt the people of Egypt, but also indicated greater suffering soon to come if Pharaoh would not relent.
Given that, Pharaoh’s response was incredibly arrogant and foolish. Pharaoh had his magicians repeat the same transfiguration, apparently turning some other vessel or body of water into blood like Aaron and Moses had. In essence, Pharaoh was accepting the challenge! He showed that he intended to literally return blood for blood. He was inviting God to continue His campaign against Egypt, and Pharaoh would most assuredly get what he asked for!
In the following verses we learn that the curse continued for a full seven days, a symbolic and holy number, a full measure of time. A week without water is fatal, and we hear how the people resorted to digging in the soil around the river, looking for something fresh. One can only imagine the crowding, the physical discomfort, and the loss of production and stability in Egypt during that time.
We are not told if, or to what extent, the Israelites were also affected by this plague. One might assume that leaving the Israelites a fresh pond of their own would only invite the Egyptians to overrun their land to reach it. I suppose God could have instructed the Israelites in ways to cure the tainted water, but we have no indication that this happened. It does seem likely that at least for some of the plagues the Israelites suffered collateral hardship. At least it was suffering for the purpose of their eventual freedom.