A few years ago, my friend was celebrating her 40th birthday with a weekend cruise to Mexico. A group of her friends were going, and many of us had never met. I was to room with one of the women, whom I'd met on only two occasions spread over about 20 years.
As the trip approached, I realized I was having some anxiety about going - more specifically, sharing a room with someone I didn't really know. It took some introspection, but it came down to this: I poo first thing in the morning. First thing.
With a thin, airplane-style door and no fan, there is nothing disguise noises or diffuse odors. Perfume? Too noxious. Matches? Too obvious. Multiple flushes? Dead giveaway with potential clogging risks. My plan was to see if there were public restrooms on the same level, but no luck - they were two levels up and too far to risk it.
I considered being direct, "Hi Kim! Great to see you again! By the way, the first thing I do in the morning is poo. You know, drop the kids off at the pool? Lay some cable? Looking forward to sharing a cabin - it's gonna be great!" In the end, it didn't matter - she was up and gone each of the three mornings before I'd even woken up. Thank heavens for small favors.
To my relief, I have since found a solution: http://www.getyougogirl.com/ Give it a try! I'd love to hear how it comes out for you in the end.