This verse repeats details already explained in the LORD’s command to Moses in verse 18. The fish included all species plus other living creatures in the river. They died as a result of the water changing into blood. The Nile became foul means that the river began to stink because of the dead fish. So that is simply the conjunction waw in the Hebrew, so the text does not clearly explain why the Egyptians could not drink. Most translations interpret this as the direct result of the odor rather than the pollution. (See verse 18 and the comment in the last paragraph.) Thus Good News Translation has “it smelled so bad that the Egyptians could not drink from it.”

There was blood throughout all the land of Egypt refers back to verse 19, where all the water in pools and in vessels was to be changed into blood. This is a general statement that may be understood to say that “everywhere in Egypt” (Good News Translation) the water became blood. Similarly Contemporary English Version has “Blood was everywhere in Egypt.”

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .