Annihilating The Nile

The Gemorah (Sotah 12b) says that when  the daughter of Pharaoh went to wash in the river, she was going to wash off from the avodah zarah in her father's house.  Rashi says that she was immersing herself as part of the conversion process.  We see from Rashi that there was the concept of gerus pre-mattan torah.  Now this might not be such a novelty, for Rashi already told us in Lech Lecha that Avrohom and Sarah converted people (though one might argue that wasn't in a halachik sense, rather they taught them monotheism, see interesting idea here.) However, if there was such a process why didn't Moshe have Tzipporah undergo this form of gerus, yet Rashi Sanhedrin (82a) is clear that she didn't have gerus?  Another difficulty with the Rashi in Sanhedrin is how could Tzipporah have done the milah of her son if she isn't Jewish, how can she be considered part of the bris (see Avodah Zarah 27a?)  

[See the Nitziv in Megillah 13a that understands the Gemorah not that it was an immersion for gerus, rather it was the immersion a baal teshuva goes through when they repent.]

The question is how do Chazal derive that the daughter of Pharaoh had this intent, maybe she just went to cool off from the hot Egyptian sun?  Rov Dovid Solovetchik explains based upon a story with his father.  When the family was running during the war, they were on a ship and of course didn't eat anything.  One of the people serving the food badgered them about their lack of eating and agreed to use new utensils and cook them rice.  The Briskor Rav relented and sent one of his sons to start the fire to avoid bishul akum.  The man preparing the food said its unnecessary, I'm a Jew! The Briskor Rav said he had an inkling this was the case, for it didn't make sense to him why this person cared so much about them.  If he was Jewish, it’s understandable that it was built into his DNA to be a nice person. Says Rav Dovid, Chazal understood if the daughter of Pharaoh was having such compassion on a stranger's child, it must be she was rejecting avodah zarah.  Now I understood some readers will like this idea, but it seems quite crazy to me.  Do you mean to say that your average goy will just abandon a baby that needs help?  The only people in the world that have any iota of compassion are Jews?  

The question though still remains, where do Chazal see to say such a derasha?  The Torah Temimah explains since the Nile was worshiped by the Egyptians it wouldn't be a place where one would go to just cool off, that would be denigrating to the avodah zarah.  If she was bathing in the Nile it demonstrated a rejection of the avodah zarah.  This point has a halachik ramification as well. The possuk says that Yocheved placed Moshe at the edge of the river (2:3) but in possuk 5 the daughter of Pharaoh finds Moshe in the water.  Was he next to the water or in the water?  The Rogatchover explains that Yocheved didn't want to use the Nile River for it was used as adodah zarah so she placed Moshe next to the river.  However, after bas Pharaoh was mebatel the avodah zarah by using it in a demeaning manner, it became permissible to benefit from the Nile and Moshe through Divine intervention was pushed into the river. 

The bittul of the Nile isn’t just a halachik bittul, it is also a theological bittul.  The avodah zarah of the Nile was the pursuit of gashmious.  When Pharaoh decrees that all the sons should be thrown in the Nile, he is ordering to drown Klal Yisroel in the pursuit of gashmious.  It is the Nile leading to the saving of Klal Yisroel that is the ultimate defeat of this plan.  It is Moshe Rabbenu (and there is a little Moshe inside everyone see Tanya chapter 42,) who gives us the capability to float and not get drowned in the mayim rabim (וד"ל) of gashmious pursuits (based on Likutay Sichos volume 16.)