Train to Venice from Rome

Buying ahead of time online would allow you to buy discounted Economy and SuperEconomy fares instead of the Base (full) fare, however those discounted fares are restricted (non refundable and non changeable) therefore if your boat is late and miss the specific train you book online, you lose the money. If you still intend to buy online a discounted ticket, give yourself enough cushion in case of delays in ship arrival/unloading.

The first step is either a Regional (unreserved) or InterCity train from Civitavecchia to Roma Termini station, then a faster, reserved train to Venezia S. Lucia station. There's no deadline to buy these tickets, so buying in the station is always possible. Booking ahead for the fast train through www.trenitalia.com is cheaper, but locks you into a specific departure. Slower-train schedules are currently only published though June 11 but summer schedules are not likely to be much different.

Search above on the topic of Civitavecchia or start with these recent couple of posts:

https://community.ricksteves.com/travel-forum/italy/train-from-venice-to-civitavecchia-cruise-port

https://community.ricksteves.com/travel-forum/italy/civitavecchia-to-rome-by-train

If you have Rick's book for either Italy or Med Cruise Ports, see also the Rome chapter there.

From the Civitavecchia (Rome) port you need a train to Rome Termini, then you'd change to the high speed Freccia train to Venice. The first leg from Civitavecchia to Rome is about 1 hour (+/- 20 min depending on type of train). The leg from Rome Termini (the main station) to Venice Santa Lucia is 3h45m.

Go to Romeinrome.com for the detailed description for getting between Civit... and Rome. You ship will drop you at the entrance to the Port. From there it is about a ten min walk to the train station. Follow the crowd, hundreds will be headed that way. You could prebook (on line) a ticket from Rome to Venice leaving around noon. That would give you plenty of time to get off the ship and make you way to Termini in Rome. I think there is a train about every hour to Venice.

Second, -- Critical ---- somewhere else in Italy, at any train station, travel agency, etc., buy a Regionale train ticket from Civit.. to Rome. The line at the Civit... train station to buy a ticket could be longer than the ride to Rome because half your shipmates are doing the same thing and there could be another ship or two in port. If you have your ticket, you walk pass the crowd, validate (time stamp) you ticket in one of the yellow/blue/green boxes on the track side of the station and get on the next R train to Rome. Non reserved, no seat - stand till one comes open.

When you get to Rome either buy your ticket or pull out the ticket your purchase. Check the departure board for your train number, get platform number, time, and walk to your Venice train. If early there are places to buy snacks for the train. Enjoy the ride.

In the case of buying a regionale ticket from Civitavecchia to Roma Termini, I would buy it online a day or so before you arrive in port. You won't save any money but your ticket will be valid for six hours from the time of your departure. The ticket will be emailed to you, you can print it out onboard the ship or just show the conductor your e-ticket on the train.