If you want non-stop you have one choice - AirTran out of GPT to FLL. You'd have to fly down the day before the cruise since the lone flight leaves Gulfport at 4:30pm and arrives in FLL at 7:13pm. Of course, flying down a day before the cruise is always a good idea.
The lone return flight leaves FLL at 3:13pm and gets into GPT at 4:03pm. These really aren't too bad of connections. About $350 per person though. The price you pay for using small airports.
Nothing from MOB is non-stop.