I don't remember any shuttles at all. I think we walked from the ship all the way to the train station, which took about 15 minutes, tops. I'm cheap.
Here is the visual on how to get from the Port of Civitavecchia to the train station and how to get there.
It's very simple. Just remember to stamp your ticket (whichever you decide to purchase).
https://sites.google.com/site/sctap...tenuto-della-app/rome-by-train/things-to-know
I forgot to mention that you can purchase tickets in advance online, but it was not necessary. We purchased our at the newsstand inside the train station.
We also purchased the BIRG tickets so that we can use the METRO and buses.
We caught the express train into S. Pietro and walked over to the Vatican.
We hired Rome In Limo, Claudio the owner set us up with Emanuela who was our art historian guide. She was an amazing guide and got us through the entrance even forgot out tickets at the Cruise Ship. She walked up to a counter and asked them to look us up with our ID/Passports. They got our replacements and we were in.
We spent 2.5 hours in the Vatican then went over to St. Peter's Basilica. Afterwards, we took a cab over to the Colosseum and toured there as well.
Our guide walked us over three blocks and had lunch in a restaurant that was so inexpensive. Ate at the restaurant and had left-overs for 60Euros. Fed 5 of us (3 adults & 2 children) and it had drinks.
Before we left, we took the bus over to the Three Coins in the Fountain. Then, we took the hop-on-hop-off bus to tour the city really quickly before we had to get off at the Vatican and walk back to the train. We could have easily taken the bus, but it was too long.
We didn't want to miss the train. It does get crowded going back because of commuters, but it was great!. Highly recommend it.