I used to work for the now-defunct "Royal Cruise Lines" in the late 80's and early 90's. I worked in reservations, and not on the ships themselves. During this time, I took 2-3 cruises per year aboard their vessels. Although not common, sexual interludes do occur occasionally between crew and passengers (Yes, I know this to be true, and I'll end it right there). Most interaction is between two males, and does not occur in anyone's cabins. It is very discreet, and goes unnoticed by others.