Cruise boats

Question

I am wondering the following: [1] How can anyone go on any cruise that would include Shabbat [they're usually "kosher" cruises with many jews on board] since even if one leaves Wednesday and is kotzetz damim by paying his ticket beforehand - he does not beforehand agree to make the non Jew stop for Shabbat, which seems to be a requirement as brought down by the Shulchan Aruch ? [2] Assuming there is a reason why the above is not a problem, would we say that for a 'kosher' cruise, because of the ketzitzat damim the mealacha is really considered as being done for themselves [for the non jewish workers] -this seems like a sham -its explicitly being done for the jews on the trip! [3] assuming the above also is not a problem -would one only be allowed to take a cruise by leaving on wednesday or earlier in our times or has that rule changed also ? thank you.