Reb Moshe, this is a fascinating question which has occupied quite a few writers, and the interesting thing is that they do not seem to be very sure of the answer, but let us see what we can come up with, b'Ezras Hash-m.

1) Firstly, I have not found what you cite from Rashi about "b'Toch ha'Mayim" and I would be very grateful if you could explain further.

2) Secondly, it would appear from Rashi in the Mishnah (17b, v'Lo) that the special thing about Dayo is not necessarily that it fades, but rather that it does not get absorbed inside the parchment. Rashi writes that this is why Dayo is better than Kumus and Kankantum; the latter get absorbed in the Klaf and cannot be erased.

3) The first Mefaresh that I am aware of who speaks explicitly and directly about this question is Rav Shimshon Refael Hirsch zt'l in his commentary on the Chumash. He writes, "There is not erasing by the water but rather into the water." Rav Hirsch understands the words "El Mei ha'Marim" (Bamidbar 5:23) according to the simple translation "into the bitter water," not "inside the bitter water," so the crucial thing is not that the Megilah be placed into the water but rather that the letters of the Megilah should arrive in the water.

4) However, a different approach is taken by the authors of Alei Veradim on Maseches Sotah (by Rabbi Shlomo Levinstein and Rabbi Tzvi Krizer of Bnei Brak). On 18a (page 242 of the Sefer), they cite many sources on this topic. I will go through a few of these sources but will not necesarily come to the same conclusion as the authors of Alei Veradim in understanding them.

5) Possibly the earliest source cited is from the Yerushalmi Sotah 2:4, where Rebbi Yudan asked a question: "u'Machak b'Afar." The Korban ha'Edah explains that the question of the Yerushalmi is as follows: What is the law if the ink on the Megilah is erased by earth which was placed inside the water? Do we say that the earth is blacker than the ink of the Megilah and therefore it is considered that the ink has been properly erased, or do we say that it is essential that the Megilah be erased specifically by water? It appears from this that the Megilah in principle must be erased in the water in the cup but that the question of the Yerushalmi is whether it must be specifically erased by the water or whether it is sufficient to erase it in the earth placed inside the water. This suggests that the Megilah must be placed inside the water.

6) Let us now continue our inquiry concerning whether the Megilah was placed directly into the water, or whether the letters of the Megilah were scraped off outside the water and then later the ink of the letters was put into the water:

a. The Aruch ha'Shulchan (Even ha'Ezer 178:63) states explicitly, "He erases the Megilah inside the water." The Aruch ha'Shulchan clearly sides with the first possibility in our inquiry.

b. Now to the opinion of the Rambam: After the Rambam describes (in Hilchos Sotah 3:10) how the Sotah water is prepared, he writes, "And he erases the Megilah into the water" ("u'Mochek l'Tochan ha'Megilah"). In my opinion, the Rambam appears to maintain that the Megilah was placed into the water; had he ruled that the letters are scraped off outside the water, he would have written that "he erases the letters into the water." The fact that he writes that "he erases the Megilah into the water" suggests that the actual parchment is placed into the water.

c. The next source is the Tosfos Yom Tov on the Mishnayos, Sotah 2:2 (or 15b). The Mishnah states that half a "Lug" of water is placed in the cup. The Tosfos Yom Tov writes that this amount is a Halachah l'Moshe mi'Sinai. The Tosfos Yom Tov adds that what we learned on Har Sinai is that this amount of water is required in order for the writing to be erased very nicely, thoroughly and easily. This is also the reason why Rebbi Yehudah says that a Revi'is of water is sufficient because, in his opinion, less writing is required on the parchment and therefore less water is required to erase the writing, as stated by the Mishnah. The fact that there is a direct relationship between the amount of writing on the parchment and the amount of water required in order to erase the writing suggests that the letters are not scraped off the Klaf outside the water (because if they were, the erasing is not being done by the water). Rather, the erasing is actually being done by the water itself. This suggests that the parchment is actually placed inside the water.

d. I also found a phrase in the Me'iri which suggests that the Megilah was placed inside the water. This relates to the Gemara on 19b where Rav Ashi stated that if the writing on the Megilah is still recognizable, one must erase the writing again until one cannot see any trace of it. The Me'iri writes that "if

the marks of the writing are still noticeable, one must erase them again in the water until they are no longer visible." The Me'iri's words "li'Mechotah b'Mayim" -- "to erase it in the water" -- imply that the erasing is done inside the water.

So far, the proofs that I have cited were to show that the Megilah was placed inside the water, but in my next reply, b'Siyata di'Shemaya, I hope to cite sources that the letters were scraped off outside the water, and I will try to reconcile the different explanations.

Kol Tuv,

Dovid Bloom