Yeah, I'd say what cruise line you're on and how long the trip is matters the most. Destination might matter a little.

We have a single friend who goes cruising with us occasionally. She's been hit on that I saw on our last cruise together. It wasn't, uh, subtle, but that guy was on the WRONG ship for it. Cruise line not known for partying (and a slightly older population in general) and in Alaska, where everyone was pretty covered up.

Now, a cruise to the Caribbean, Mexico, or Mediterranean... especially a shorter trip... On something like Carnival or Norwegian... I expect a lot of hooking up.