May I participate in a cruise that travels over Shabbos?

Chazal taught in a beraisa that one may not set sail on a sea voyage within three days of Shabbos. This applies only to a voluntary trip; for a mitzvah, one may sail even on erev Shabbos.¹ While some hold the restriction begins only Wednesday night, the Alter Rebbe holds it begins already on Tuesday night.²

The Rishonim explain that travel on saltwater seas leaves a person shaken and disoriented by the rocking of the ship, and it takes three full days for the body to settle. Setting out any closer to Shabbos means one won’t enjoy oneg Shabbos. On freshwater rivers, where there is no such discomfort, one may sail even on erev Shabbos (but if setting out from Wednesday on, one should stipulate with the operator to rest on Shabbos).³

Since modern ships are so large and steady, some argue that this discomfort no longer happens, and that a cruise should be treated like a freshwater voyage. They point to the Meiri, who exempts sailors and others used to the sea who feel no distress.⁴ In practice, though, people still get seasick, and it usually takes about two days to adjust. There is also a real difference between a seasoned crew and ordinary passengers. Thus, for a recreational cruise, the three-day rule would apparently still stand.

When a sea voyage within three days of Shabbos is permitted for a mitzvah, one must stipulate with the operators to rest on Shabbos, even if they don’t end up stopping.⁵ But if it’s known that the Jew will have to be mechallel Shabbos (even an issur derabanan) for pikuach nefesh, setting out from Wednesday on appears like intentionally entering a situation of chilul Shabbos, and is forbidden.⁶

A bigger concern applies today, regardless of when one sets out. Modern ships run on electricity, steam, and other melachos forbidden on Shabbos. If the owner, crew, or sailors are Jewish, sailing is forbidden even on a Sunday departure, unless the ship drops anchor and shuts down completely for all of Shabbos.⁷ If the ship is owned and run completely by non-Jews on a fixed route and schedule, it is permitted even when most passengers are Jewish. But if the trip runs only because Jewish passengers fill a required quota, the melachos count as done for them, and it is forbidden. Either way, one must be careful about melachos done specifically for him and about the rules of amira l’akum.⁸

Today, when one can now travel anywhere midweek by plane and avoid Shabbos travel, some discourage being aboard over Shabbos when there is no need.⁹

See Sources (open PDF)