You could check the website of Greek railways https://www.hellenictrain.gr/ for trains. For ships, I do not know wich are included.

hellenictrain.gr seems to be the best option but as I’ve seen myself it isn’t accurate…

I wanted to go to Litochoro and the both cashier I went to see on two different days at thessaloniki train station told me there was no train going/stopping there. Took a bus instead which they issued a ticket for.

To then go to Athens, I had to take another bus to Katerini and wait for one of the two daily trains they have running at the moment form Thessaloniki to Athens.

Turns out those trains actually stop in every city you can think of (or pretty much). They clearly don’t know what the heck is going on and the website clearly tells you it doesn’t exist either.

Seems like one should question everything people tell you here in Greece… I’ve been through the Balkans and things seemed much clearer, also I didn’t feel like a cashcow like here where people just want your euros and will only give you the most expensive option. Be on the lookout and anticipate as much as you can and as I said, question everything people tell you.