95:17 Regarding a case where a non-Jew brought fruit and there is no concern that it was picked on Shabbos, and similarly with other items where we have no concern that forbidden labor was performed on Shabbos, except that this fruit or these items were brought from outside the Shabbos boundary:
If the non-Jew brought these things for himself or for another non-Jew, they are permitted to the Jew immediately, even for eating. However, they may only be carried four cubits unless they were brought into the house or the city has an eiruv. In that case, it would be permitted to carry them throughout the city. This is because every place where it is permitted to carry is considered like being inside four cubits.
If the non-Jew brought these things from outside the Shabbos boundary for a Jew, it is forbidden for this Jew and his entire household to use them until a sufficient amount of time after nightfall, which is the time it would take to bring these things. (If the non-Jew brought one Jew an apple and another Jew an orange, the two Jews are not allowed to trade in order to enjoy immediate use – Mishnah Brurah 325:37.) In any event, one may carry within his personal four cubits or in a place where it is permitted to carry.
If it’s not known whether or not these items were brought in from outside the boundary, it is also prohibited to use them unless it’s more likely that they were not brought in from outside the boundary. (If something is not used on Shabbos because of doubt, it may be used immediately after Shabbos without waiting – MB 325:48.)
95:18 We have a tradition that there are no boundaries above ten handbreadths high. Therefore, if a person boarded a ship on Friday before Shabbos started and the ship traveled even a great distance, nevertheless when he arrives in the harbor on Shabbos and disembarks, he has from there 2,000 cubits in each direction. This is because we assume that during his voyage by sea, he was always more than ten handbreadths from the ground and therefore he never acquired a “home base” for Shabbos until he reached dry land. However, if he left the ship and returned to it on Shabbos, since he acquired his “home base” on land, if the ship then traveled outside the boundary, he is now limited to the four cubits that are given to a person who travels outside the Shabbos boundary. (If circumstances later force him to disembark and enter a city, he may freely travel throughout the city – Rema 404:1.) Similarly, if the ship was in a place on Shabbos where there aren’t ten handbreadths to the ground, the passenger acquired his Shabbos “home base” there. If a person is unsure whether or not this is the case, he should act leniently in this matter.