I just got home from a seven day cruise to Bermuda. My traveling companion was my 14 year old nephew. Actually, "companion" is not really an appropriate word, since I rarely saw him. He was off with the teen club and his new friends whenever he could. The NCL cruises are great for parents who don't want to see their kids much.
Basically, I was a single traveler on a cruise with no particular facilities or activities for adult singles, so I had to put some effort into enjoying myself. And enjoy myself I did. I spent a small fortune in the spa and racked up an epic bar bill. Gambling accounted for a few hundred bucks, and it was money well spent. I managed to find dance partners most of the time. On two evenings I had dates with women I met on the ship. Alas, there was no Love Boat happy ending where Gopher brings the star crossed lovers together.
I was delighted with the service and the friendliness of the crew. I met a lot of nice people who let me hang around with them. My only complaint would be that most of the passengers were of a lower social class than I am accustomed to hanging around with, so many of them were loud and obnoxious and whiny and constantly complaining about everything. I wanted to throw them overboard.
I don't think I'll take a cruise as a single person again unless it's explicitly a "Singles' Cruise".