Explanation: This is not an episode that contradicts [the Halachah taught], for it refers to above (86a), that [R. Yehudah] does not require a Mechitzah for the sake of water. (Tosfos Yom Tov - in the text of our Mishnah of Tosfos, other Rishonim and the Yerushalmi, R. Yehudah only brings the episode. He does not say "the wall on top...")

Observation: Above (76b), Rav held oppositely, that in Reshuyos mid'Rabanan, when the wall between two Chatzeros is not four wide, he may not move even a hair's breadth, for [Chachamim] strengthened their words more than Torah law.

Question: Below (101b) it connotes that Rav Dimi forbids transferring even between Reshuyos mid'Rabanan, regarding a Beraisa there;

Citation (101b - Beraisa - Chachamim): Even when the lock is above 10, he brings the key before Shabbos and places it in the porch, and on Shabbos he opens and locks with it and returns it to the porch or the window over the opening;

[It says that] if the window is four by four, it is forbidden, for he is like one who is Motzi from Reshus to Reshus, i.e. from the porch, which is Karmelis, to the window, which is Reshus ha'Yachid, through the lock, which is Mekom Petur, and it is forbidden to transfer.

We conclude that this teaches that Rav Dimi's law is correct!

Answer: Surely, Rav Dimi holds that the Beraisa below argues with [the Beraisa] of our Sugya. [The Gemara there] means as follows. Rav Dimi's law is correct, and even more than he taught. Even Reshuyos mid'Rabanan, one may not transfer between them, like Ze'iri in our Sugya.

Implied question: The Beraisa below (101b) is like [Ze'iri! Why is it difficult if this Beraisa is unlike him?]

Answer: Even so, [the Gemara] wants to establish also this Beraisa like him.

Observation (Ri): However, Ze'iri is unlike R. Yehudah, who permits in Shabbos (101a) in a boat that is 10 high (above the water) and 10 deep (so it is Reshus ha'Yachid) to transfer from it to the sea and vice-versa via above 10, which is Mekom Petur.

Reference: I explained this above (86b DH Gezuztra. Even without a Mechitzah, the balcony itself is Reshus ha'Yachid, and one may carry in all of it.)

Question (Ri): Here we require a Mechitzah. In Shabbos (100b), Rav Huna said that for a boat, one extends a ledge Kol she'Hu and draws [water]!

Answer #1 (Ri): There, the water is 10 deep, for we say that a boat does not go in water less than 10. We measure Karmelis from the ground, and the water, above 10, is Mekom Petur;

Here, the water is not 10 deep. When we say that we measure from the ground, the water is still Karmelis.

Answer #2: Even if the water is 10 deep, they decreed due to other balconies that do not have [water] 10 deep under them. There, a Mechitzah is needed [to permit] to draw. Therefore, [Chachamim] did not distinguish regarding any balcony;

However, a boat always goes in water above 10 (so there is no reason to decree).

Answer #3 (Ri): Here, even if [the water] is deep, there is concern lest the sea deposit debris (and then the water will not be 10 above the ground);

However, a boat always goes (and they are careful that it not go in water less than 10), so there is no reason to be concerned for this.

Implied question: in Shabbos (100b), Rabah bar Rav Huna taught that he makes a place four [by four Tefachim] and draws [water]!

Answer: This refers to through Mechitzos of 10 [Tefachim]. Therefore, we require a place four, like Rashi explained above (86a DH Korah), that there is no Mechitzah for less than four, and unlike Rashi explained there (that short walls suffice).

Inference: Rashi connotes that "above" is above the balcony, and "below" is below the balcony.

Explanation: He did not want to explain that everything is below the balcony, like "above and below" above (86a) regarding a pit, because a hole four by four and he makes a Mechitzah around the hole, even above it is a Heker.

Implied question: Chananyah said only regarding the lake of Tiverya!

Answer: Our Mishnah does not distinguish, and discusses all bodies of water.