Serial killer. Cruises are rige with them.
Rige=rife
The balcony railing in cabins is not very high. If one is drunk, and tries to look down over the railing, one can lose balance and fall.
The ships move at 20-25 knots. In dark time of day, by the time they discover you are missing, the ship would be gone 20-30-40 miles away.
I was recently on a cruise, when a young girl fell overboard. She was drunk. She was very lucky because it was full moon night and the ship was purposely going slow due to being ahead of schedule. Her boy friend saw her fall, and threw a life saver devidce to her, and the ships crew began search immediately and they found her.