Never -ever fall for a free cruise scam. While some of then may be just timeshare pitches - that is the best-case scenario.
Worst case, you make end up being taken for thousands of dollars.
If a solicitor calls you and says you have won a free cruise - (especially if you entered at a state fair or the like) do not fall for this. They will ask for a credit card for "taxes & fees" and then proceed to bill it for far more than you expected.
Then you will find out all the possible travel dates are restricted (meaning you pay if you want them), that you only have a year to take this cruise, and that even if you do not go you may have your card charged up to a year later for the cruise you did not take - this is in addition to the $1000s they have already billed you for deposits, etc.
Just stay away - there are too many reputable companies out there selling real cruises at bargain prices. Nothing is free.