(א) "ויקח את בת לוי" - פרוש היה ממנה מפני גזירת פרעה (וחזר ולקחה וזהו וילך שהלך בעצת בתו שאמרה לו גזרתך קשה משל פרעה אם פרעה גזר על הזכרים ואתה ג"כ על הנקבות והחזירה ועשה בה לקוחין שניים...
and married a daughter of Levi: He was separated from her because of Pharaoh’s decree and he remarried her. This is the meaning of "went", that he followed [lit., he went after] his daughter’s advice that she said to him, Your decree is harsher than פַּרְעֹה. Whereas Pharaoh issued a decree [only] against the males, you [issued a decree] against the females as well [for none will be born], and he took her back and married her a second time....
And there went a man of the house of Levi. Where did he go? R. Judah b. Zebina said that he followed [lit. went] the counsel of his daughter. A Tanna taught: Amram was the greatest man of his generation; when he saw that the wicked Pharaoh had decreed 'Every son that is born ye shall cast into the river', he said: In vain do we labor. He arose and divorced his wife. All [the Israelites] thereupon arose and divorced their wives. His daughter said to him, 'Father, your decree is harsher than Pharaoh's; because Pharaoh decreed only against the males whereas you have decreed against the males and females. Pharaoh only decreed concerning this world whereas you have decreed concerning this world and the World to Come. In the case of the wicked Pharaoh there is a doubt whether his decree will be fulfilled or not, whereas in your case, though you are righteous, it is certain that your decree will be fulfilled, as it is said: Thou shalt also decree a thing, and it shall be established unto thee! He arose and took his wife back; and they all arose and took their wives back.
(3) And when she could not longer hide him, she took for him an ark of bulrushes, and daubed it with slime and with pitch; and she put the child therein, and laid it in the flags by the river’s brink. (4) And his sister stood afar off, to know what would be done to him.
When everything seems bleak, Miriam has hope!
had no water: From here [we learn that] all forty years they had the well in Miriam’s merit.
Three good leaders had arisen for Israel, namely, Moses, Aaron and Miriam, and for their sake three good things were conferred [upon Israel], namely, the Well, the Pillar of Cloud and the Manna. The Well, for the merit of Miriam; the Pillar of Cloud for the merit of Aaron; the Manna for the merit of Moses. When Miriam died the well disappeared, as it is said, And Miriam died there, and immediately follows [the verse], And therewas no water for the congregation; and it returned for the merit of the [latter] two.
Maybe they didn't lose water, but really hope! Hope in a bleak place is like water in the desert. And it was Moshe's job to restore that hope. What did Moshe tell them instead?