The cruise ships motion should not be any issue, the big ships are quite stable. They have stabilizing fins other ships don't, the swimming pool water does not even slosh.
Possibly excepting storms, it will be comparable to other hand holding situations. They are in port most of the days anyway. On the top deck in the sun won't be any issue. About the only issue to expect is that indoors in the various lighting, white balance will be the issue.