The Kerias yam suf, receiving of the man, shlav, and mayim in the midbar, and milchemes amalek, are all found in Parshas Beshalach. These incidents occur within the span of a few weeks- but are they related to one another merely by their chronological proximity, or is the Torah trying to teach us a deeper message by juxtaposing these three incidents?
The Kerias yam suf, the epitome of a nes nigleh - a revealed miracle, was the culmination of the miraculous events surrounding yetzias mitzrayim. The Torah addressed the two reactions people might have to such an event.
Most people who experience an open miracle recognize it as being the hand of Hashem but there are always some who are skeptical. How could Amalek attack the Jewish people so soon after krias yam suf? Did Amalek not realize they were trying to destroy a nation that had open miracles performed for them? Amalek closed their eyes to the miraculous events of yetzias mitzrayim by explaining them away as mere natural occurrences. Amalek is described in Parshas Ki Teisei as the nation, "Asher karcha baderech" - their entire philosophy was that everything was a mikreh - a coincidental happening. If one views everything as a coincidence even krias yam suf can be explained away as a bizarre natural even that happened to take place at the right time. If one chooses to deny the obvious hand of Hashem one can deny every miracle by calling it nature.
There is another possible reaction to a miracle. One acknowledges the miracle as being the work of Hashem but views the event as a one-time demonstration of the involvement of Hashem in this world. The Ramban in Parshas Bo explains that the ultimate purpose of a revealed miracle is to enable people to realize that they are surrounded by miracles every day. What the world calls nature is also a miracle. Chazal teach us that to recite Hallel daily is inappropriate whereas to say Ashrei everyday is praiseworthy. The Meshech Chochma explains that the theme of Hallel is praising Hashem for revealed miraculous events. Ashrei, which says, "poseach es yodecha umasbea l'chol chai ratson" ("you [God] open up your hands and satisfy all living creature's needs") is the ultimate praise for parnasa. Hashem takes care of our daily needs through seemingly natural ways. Ashrei teaches us to recognize Hashem even in the "natural" miracles that surround us daily. One who says Hallel daily but neglects the everyday saying of Ashrei demonstrates that he only recognizes Hashem's "extraordinary" miracles but fails to see the miracles of everyday life.
To combat this reaction to miracles, the story of krias yam suf is immediately followed by the events of the slav, man, and the finding of water in the desert. Hashem, who performs great miracles, also provides for our daily needs such as food and water. We are required to elevate the world by always seeing our attainment of parnasa, and the natural world in general as miraculous.