Current recommendation for film for flying: Take all film on in your carryon. Do NOT send through with checked luggage, as those x-ray machines are more powerful. If your film is 800 speed or higher, put them in separate baggie and have them hand checked at all airports.
On the ship: the x-ray machines are relatively low dosage, so not much to worry about. I would recommend to try not to take the same film on and off the ship, over and over and over. X-ray exposures are cumulative effect. A few times thru the machines won't be bad, but 20 times thru might be harmful.
We found that the people at the airport were more than willing to "hand check" the high speed film...however security on the ship was not nearly as courteous as they required that all fill pass through the X Ray machines. If you're really worried about pictures not turning out because of passing through the machines too many times, you could always get the pics developed on the ship - prices are actually fairly reasonable and you make sure you at least get some pics out of the trip!!!!