I believe Hertz and Enterprise have drop offs in Galveston and then they will shuttle you to the pier. I used Enterprise. If you do, make sure you drop off your luggae at the pier before you drop the car off. They really don't want you to bring your luggae on the shuttle. Given the amount of luggage per person you can kind of understand why. So just drive to the port, drop your luggage at the ship, return the car (about a mile or 2 from the pier) and you're good to go.