Fun cruise = bullshit. There's obviously no such thing, water slide lines are long, pools are full, the cabins suck, on-board entertainment is lame, Rock Climbing Wall requires a harness, I personally don't like having my sack in a pinch. Shuffleboard? No thanks, I can do that at home. The most I'd get out of a cruise is the food and the bed. Of course if you watch the commercials you can tell those smiles are because a gun is pointed at them, and they've cried so much they can't help but smile because all of their emotions have been exhausted.
If you want a fun cruise, you have to get your own boat, a load of beer, and a bunch of people, the people who had the most fun won't make it back to shore.