Gittin 8A

העשויה לברוח, אבל עציץ, שאינו עשוי לברוח ⁠– לא.

which is made to move, i.e., it is not set in one place. Consequently, one can argue that the soil in the boat is not considered attached to the ground. However, with regard to a flowerpot, which is not made to move, as ordinarily a flowerpot remains in one place, no, one cannot reasonably claim that the fixed soil in it is not part of the ground, even when the pot itself is not touching the ground.

אי נמי: עד כאן לא קאמרי רבנן התם אלא בספינה, דלא מפסיק אוירא ⁠– דמיא כי ארעא סמיכתא דמיא; אבל עציץ, דמפסיק אוירא ⁠– לא.

Alternatively, one can say the opposite: Perhaps the Rabbis state their opinion, that the soil in the boat is considered to be like the land itself, only there, in the case of a boat, where there is no barrier of airspace between the soil in the boat and the land below, as water is considered to be like solid earth. Therefore, the soil in the boat is viewed as connected to the earth, and has the status of Eretz Yisrael. But in the case of a perforated pot, where there is a barrier of airspace, no, the soil is not connected to the ground.

רב נחמן בר יצחק אמר: בנהרות דארץ ישראל דכולי עלמא לא פליגי. אלא כי פליגי ⁠– בים הגדול.

Rav Naḥman bar Yitzḥak said: With regard to the rivers that are in Eretz Yisrael on which a boat is sailing, everyone agrees that a bill of divorce written on that boat is considered to be written in Eretz Yisrael. However, when they disagree it is with regard to the Great Sea, i.e., the Mediterranean Sea. In other words, is a boat located in the Mediterranean Sea considered to be in Eretz Yisrael or not?