1)
Why does it say that they could not drink the river water due to the stench? One cannot drink blood!
1.
Bechor Shor (cited in Hadar Zekenim and Riva, verse 17): It turned to blood only temporarily. When it returned to water, they could not drink it only due to the stench.
2.
Da'as Zekenim (verse 18), Riva (verse 17, 2): The water merely looked like blood. If not for the stench, they would be able to drink it.
