Are you on the Autotrain and bringing your vehicle? If yes, you can go FL-46 to I-95, or if you want to avoid I-95 (we always try to) you can go FL-417 to FL-528. Both have tolls.
If you aren't bringing a vehicle, then I agree with the previous poster that Uber XL or Lyft XL may be your best bet. You could also look into some of the private shuttle services, but read reviews online before booking.
BTW - I have done the Autotrain once from Sanford (Orlando) to Lorton. We had a 13-hour delay stuck on the tracks just south of Jacksonville because a CSX train derailed in front of us. Hope you have a decent amount of time padded between your arrival and the cruise, just in case.