Explanation: [What is the case] of Tum'as ha'Tehom? He descended to immerse in a cave due to Tum'as Sheretz, and a k'Zayis of a Mes was found floating by the opening of the cave;

It is a Safek whether there was a k'Zayis of the Mes in the cave at the time he immersed, and [the cave] towered [over it and over him], or there was not there at the time he immersed. He is Tamei, for Safek Tum'ah in Reshus ha'Yachid is Tamei.

If he found out even after he shaved, he is Tamei. We do not say that even if there was a k'Zayis of the Mes in the cave at the time he immersed, he is Tahor due to Tum'as ha'Tehom;

Since nothing was covering it, it is like a known Tum'ah.

Explanation: [If it is covered in the ground of the cave], then surely it is called Tum'as ha'Tehom. Therefore, if one descended [into the water] to cool off, and days later, after he shaved, he found out about that Tum'ah, he is Tahor, for it is Tum'as ha'Tehom.

Citation of Gemara: To become Tahor from Tum'as Mes.

Explanation: If he descended to become Tahor from Tum'as Mes, and after he returned and counted the days of Nezirus and shaved, he found out that when he descended to the cave there was a k'Zayis of a Mes covered in the ground of the cave, he is Tamei, for what has Chezkas Tum'ah is Tamei;

The tradition that Tum'as ha'Tehom of Mes is permitted, this is only for a person who did not have Chezkas Tum'as Mes.

Citation of Gemara: For there are Raglayim l'Davar.

Explanation: There is a great reason. We can say that since he has Chezkas Tum'as Mes, Tum'as ha'Tehom was not permitted for him.

Implied question: Why did the Reisha discuss one who descended to immerse, and the Seifa discusses one who descended to cool off?

Answer: The Reisha teaches a bigger Chidush. Even though he descended to immerse, and presumably he was meticulous and checked well that there is no Tum'ah around him, and [afterwards] a Mes was found floating at the opening of the cave...

Even so, he is Tamei, because this is Safek Tum'ah in Reshus ha'Yachid.

Also the Seifa teaches a bigger Chidush. Even though he descended to cool off, and he does not normally check around him, even so, when [a k'Zayis of a Mes was found] covered in the ground of the cave, he is Tahor, for it is Tum'as ha'Tehom.

Explanation: Regarding one who offers Pesach it says "Ish Ish Ki Yihyeh Tamei la'Nefesh Oh v'Derech Rechokah Lachem." Since it put "Tamei la'Nefesh" next to Derech, we say that it is like a road. We learn Nazir from one who offers Pesach.

Observation: In Pesachim (81b), the Gemara does not say so. There is it says "what is clear to him";

Citation (81b): We find this regarding a Nazir. What is the source for one who offers Pesach? It says "Oh v'Derech Rechokah" - like a road...

Inference: They do not argue, and they do not learn from Nazir from one who offers Pesach [rather, they learn one who offers Pesach from Nazir]!

Explanation: [Tiglachas is Me'akev him] from drinking wine. According to Rabanan, who say that Tiglachas is not Me'akev, if so, once one of the bloods was thrown, he is no longer considered a Nazir;

Similarly, when he found out before shaving, it is as if he shaved.

Question: In Pesachim (81b), Mar bar Rav Ashi said that Tum'as ha'Tehom is Meratzeh (makes acceptable) even if he found out before Zerikah;

Now, [like whom is this]? If it is like R. Eliezer, even after Zerikah, [Yedi'ah, i.e. finding out that he became Tamei] is Soser before shaving!

And if it is like Rabanan, before Zerikah, which is Me'akev according to Rabanan [like shaving is according to R. Eliezer, so Yedi'ah is Soser] like before shaving according to R. Eliezer! Here it connotes that [Yedi'ah before] something that is Me'akev is Soser according to everyone.

Answer: We discuss one who offers Pesach. He need not shave. It is like both Rabanan and R. Eliezer;

Explanation #1: Once Pesach was slaughtered, the blood is destined to be thrown, and anything destined to be thrown, it is as if it was thrown. Therefore, [Yedi'ah] is not Soser (does not cause that he was not Yotzei Pesach), since it was slaughtered;

However, shaving is a Mitzvah by itself. (It is not connected to Zerikah, so we cannot say that it is as if Zerikah and Tiglachas were done.)

Explanation #2: This that we say there that Tum'as ha'Tehom is Meratzeh, i.e. the Tzitz is Meratzeh. Therefore, it is Meratzeh even before Zerikah [of Pesach];

However, Ritzuy of the Tzitz does not apply to Tiglachas. (It is Meratzeh only for blood, Chelev and meat - Pesachim 16b.)

Explanation: [If Toch Melos he became Tamei] through a known Tum'ah or Tum'as ha'Tehom, and he found out after Melos before shaving, according to R. Eliezer, what is the law?

Does it depend on the time of the Tum'ah, and he cancels 30 days?

Or, does it depend on the time of Yedi'ah, and he cancels seven days?

Question: Why do we say [that he need not teach that it is Soser? The Tana] needs to teach that there is a Tum'as ha'Tehom that is Soser, e.g. he found out before he shaved!

Answer: He infers [the law of one who found out after Melos] from the superfluous clause (the Seifa) in the Mishnah. We already know [about one who found out Toch Melos] from an inference from the Reisha, which says "he found out after he shaved."

Explanation: [In Kelim means that] there is water in a Kli, and a Sheretz floats on the water. It is a Safek whether or not he touched the Sheretz. "Or in land", i.e. [a Sheretz floats] on water on land. [In both cases,] he is Tahor;

R. Shimon says, in a Kli he is Tamei. In land he is Tahor.

Distinction: If he surely touched, he is Tamei [for touching] in any place where it swarms.

If it is a Safek whether or not he touched, only on the ground he is Tamei, if it is Tum'ah in Reshus ha'Yachid, but floating, which is not fixed, he is not [Tamei];

We have a Safek whether only on water we are Metaher, or if the same applies to floating in the air, that a person throws it in the air. [Perhaps] we are Metaher due to the exclusion "Al ha'Aretz."