Typically, cruises book their rooms with a per-person, double occupancy rate. In other words, it's a room for two. So when a single person goes on a cruise, they'll have to pay a singles supplement -- a fee which runs anywhere from 110 percent to 200 percent of the per person rate. There are single share programs, where cruises offer to match you up with a roommate of the same sex and smoking preference. But who wants to share a room with a stranger on vacation? Some senior cruises waive the singles supplement, so pull out your AARP card and hit the open sea!