Shuttle bus is a no no
I want to add to the above post based on substantial experience. For those going to Florence by train, a taxi from the ship is the way to go! There will often be some resistance on the part of taxis that do not want to take the short haul (they do charge about 25 Euros for the taxi) but if you are politely assertive you will usually find a taxi to the station. If you get off the ship as soon as possible you have a good chance of making an early train (before 8am) thus giving you a longer day in Florence. The Shutt1le buses are a joke since (as mentioned above) they usually do not run before 8 (often not until at least 8:30) and will not take you near the train station. By the time you pay for the shuttle (most cruise lines charge) and use a taxi or bus in town it will cost you nearly as much as a taxi to get to the station. There are trains at 7:30. 7:43, 8:12, 8:29 (change at Pisa) and 9:11. If you use the shuttle you may not even make that 9:06 which means your next train is not until 10:10 and you would not get to Florence until 11:30. Meanwhile, those who grabbed an early taxi will probably be in Florence by 9:30. Enough said.