Traveling by Sea and River In European Lands
The arrival of Jews in Europe signified a change in the physical conditions under which Jews lived, and many of the problems that had plagued earlier generations vanished almost automatically. Jews living in Europe no longer made a living by farming; we no longer hear of difficulties in irrigating fields or harvesting the fruits of the land on the Sabbath. Nevertheless, the kind of occupations typical of European Jewry involved contact with Gentiles, and these contacts gave rise to problems that did not always have a precedent in geonic tradition. Furthermore, the sages of these generations refused to recognize the absolute authority enjoyed by the geonim, preferring to refer to talmudic sources for acceptable solutions to questions they might have resolved in accordance with geonic instructions.
The integration of these two factors, the change in physical reality and the independent interpretation and ruling of scholars living outside Babylonia, is especially illustrated in the problem of traveling by boat on the Sabbath. In contrast to Babylonia, where traveling by river was considered forbidden, Maimonides testifies that the scholars of Spain used to sail along the Guadalquivir River and from there to Alexandria