פירוש על שמות 7:18

ונלאו מצרים THE EGYPTIANS SHALL WEARY THEMSELVES in seeking a cure for the waters of the river that they may become fitted for drinking.

ונלאו, I explained the origin of this word already on Genesis 19,11. It is a reinforced version of saying “they could not.” It is an expression of being powerless.

והדגה אשר ביאור תמות, the river will not retain the appearance of a river, part of it has been turned into blood; but the entire river bed will be filled with blood so that the fish have no habitat in which to survive.