(Exodus 15:22) "and they went in the desert for three days without finding any water": R. Yehoshua says: This is to be taken literally. R. Elazar says: Wasn't there water under the feet of the Israelites, the earth floating on water, viz. (Psalms 136:6) "He spread the earth over the water"? (i.e., they could dig for it). What, then, is the intent of "without finding any water"? — (He made them dig) in order to weary them (to test their faith).