Hacham Ovadia Yosef, in his work Hazon Ovadia (vol. 1, p. 112; listen to audio recording for precise citation), addresses the question of whether one may ride on a freight ship driven by Jews on Shabbat. Many freight ships owned by Israeli companies continue sailing on Shabbat, and the drivers are non-observant Jews. Driving a ship, as Hacham Ovadia notes, involves numerous different Shabbat violations, and is thus clearly forbidden. Is one allowed to be a passenger on such a ship, which is being steered by a Jew in violation of Shabbat?
Hacham Ovadia cites a letter written by the late Lubavitcher Rebbe (Rabbi Menachem Mendel Schneerson, 1902-1994) to Israeli Rabbis establishing that it is forbidden to ride on such a ship on Shabbat. The Rebbe noted that after considerable research he found that it is perfectly safe for a ship to dock at a port, or to simply stop, for Shabbat. There are thus no grounds for allowing the voyage to continue on Shabbat for "Piku’ah Nefesh" (in the interest of saving lives). And although some people think that a ship can sail automatically, and thus does not necessarily entail Shabbat desecration, the Rebbe determined that this is simply incorrect. Accordingly, driving a ship clearly constitutes a violation of Shabbat, and each passenger contributes to the violation by virtue of his body weight, which requires the engine to work harder. The Rebbe thus concluded that it is forbidden to ride on Shabbat on a ship driven by a Jew.
The Rebbe further noted the argument advanced by some that the ship has to continue sailing on Shabbat in order to avoid severe financial losses that would be caused by delayed shipments. Clearly, however, this concern does not justify Shabbat desecration. The Rebbe compared this argument to somebody who tries putting out a fire by pouring benzene on it. Shabbat violation causes much greater damage than any losses incurred by a delayed shipment. And thus just as a Jew may not allow his factory to operate on Shabbat, despite the losses he will incur by shutting it down for Shabbat, similarly, it is certainly forbidden to sail a ship on Shabbat to avoid financial losses.
Rav Moshe Feinstein (Russia-New York, 1895-1986), in his work Iggerot Moshe (Orah Haim 92), disagreed, and allowed riding a ship on Shabbat even if it is driven by a Jew. He notes the Halacha allowing one to board a ship that is driven by a gentile before Thursday, even though it will continue sailing on Shabbat and the trip may pose life-threatening situations necessitating the desecration of Shabbat. Rav Moshe contends that riding a ship steered by non-observant Jews on Shabbat should be no different. Hacham Ovadia, however, rejects this claim, noting that there is a clear distinction between the two cases. The Halacha mentioned by Rav Moshe allows boarding a ship despite the possibility of a "Piku’ah Nefesh" situation surfacing. In the case under discussion, however, a Jew is steering the ship in violation of Shabbat despite the fact that there is no "Pikua’h Nefesh" at stake. Hacham Ovadia rules that this would be strictly forbidden, since one’s presence on the ship increases the Shabbat desecration. Therefore, one should not travel on Shabbat on a ship driven by Jews, and should instead ensure that if he travels by boat that it is driven by a non-Jew.
Summary: One may not ride on a boat that sails on Shabbat and is driven by a Jew.
