Are cruises a good place to hook-up for singles?

It depends on several factors. Including the Cruise Line, your age, when you are going, and your Itinerary.

Some cruise lines cater to older demographic that may have very few singles. So on a cruise like this you may have one "Singles Mixer" in one of the night clubs one evening. But on cruises that cater to a younger(and tend to be more single) crowd you may get nightly mixers, as well as activities during the day.

The other thing is the Itinerary. Cruises attract International Passengers, so depending on the cruise you are on you may have several people from different States and even Countries(which makes a long term connection a bit tougher). Although, if you are going in December, I figure you are going to the Caribbean or Bahama's which will probably consist of mostly people from the US.