When I worked on the Norway there was a large singles group cruise company that would bring singles onboard every few weeks - those cruises were always a little crazier.
Yes - large groups can be very moody, either in a good way or a bad way.
The Jazz Cruises, by the way, are the best cruisers I have ever been on in terms of just pleasant overall friendliness, and best of all, they are also the most racially mixed cruises, but jazz lovers (and these are all serious jazz lovers) tend to have a deep appreciation and knowledge of music, so you have something to share with everyone on board - and race truly is a non-issue no matter what.
Neither is age. I remember older white men telling young black guys how much they not only admire them, but love them.
I was on the last cruise Wayman Tisdale appeared on (and played) - he didn't look very good, but we were all told and believed he was in recovery from the leg cancer that took his leg. He did not make it to the next cruise (he passed away). But on that cruise everyone was in tears listening to his story.
He had been a Phoenix Sun and my wife had worked on him as a professional massage thearpist (and the other Suns as well for three years) - and we tried to get in to talk to him a few times but his entourage unfortunately made it somewhat impossible and we never got to talk to him. When she heard he had died she was devastated. She was really sad she didnt try harder to get in to talk to him. he was a very special person, ball player and musician.