Athens to nafplio greece

It appears that the KTEL bus takes 2 hr. 10 min. each way, so I don't think that's going to give you much time at all in Nafplio by the time you manage to debark, get to the bus departure point, wait for the next bus, and head back early enough that you are sure not to be late for the cruise departure.

Edited to add: That bus time is for Athens to Nafplio, so getting from the dock to the bus station will take some time.

It is one of the two most beautiful cities in Greece but you are too short of time to visit.

https://www.rome2rio.com/map/Pireaus/N%C3%A1fplio

Presumably the ship will dock in Pireaus, so the bus trip is a probably bit longer than what acraven suggests.

Lunch in Athens at your favorite restaurant with a view of the Acropolis looks to be the best option

Not enough time. Do the RS walking tour of Athens or the Acropolis museum or the National museum and a meal.

if you MUST go to Nafplio, hire a car and driver so you don't waste time.

Car & driver will probably cost you about €400 for 8 hrs hire: even if he sits around for 3-4 of those, while you sightsee in town, those are hours in which a taxi or pvt. car driver could be driving passengers for revenue. And then there's the gas & tolls. Since you mention taking a bus, I'm guessing that a car & driver are not in your budget.

That's the reality with a cruise; it's basically a shipboard experience, with a brief time ashore, enough to see a couple of Famous Local Sights & have lunch. The problem is, the cruises Sell themselves to prospectives with the idea "experience 5 lovely islands in 6 days!" And people want to believe it.

I'm vaguely remembering the bus had a stop closer to the docks that would save some time - but not enough. It is what it is, enough time to see the top sights of Athens - enjoy

We have just returned from Nafplio and took the bus to Athens. It was a 2 1/2 hour ride in a nice enough bus but some curves in the road so we were a bit car sick.

That's really not enough time for getting to Nafplio, seeing the town and returning. As stated it will be about a 2 hour ride each way leaving you maybe 4 hours to see the sites. Doable . . . but it will be rushed.

An alternative would be a day trip to the island of Aegina, very close to the mainland. Flying Dolphin will take maybe 40 minutes but can be a rough ride. Regular ferry about 1 1/2 hours giving you a bit more time on Aegina.

Since you are right at the port maybe you can get the ferry to Aegina. There are numerous times available and if you luck out you can get one fairly close to the time you arrive.

You say you've been to Athens before. Once, twice . . . how many times? If just one your best bet would see Athens. There is really a lot to do there, not just the main tourist sites but many other areas of the city. It will be less "stressful" getting to central Athens by taxi and dropped off at Monistiraki Square and then start wandering around.

I would go on cruisecritic.com and find your cruise and port stop Athens and see if anyone else is looking for others to share a rental car or get a group together to hire a car (or van) and driver for a private tour to Nafplio. Either way, it's important to know that you won't have more than 3 hours in Nafplio so the time and cost may not be worth it.

I think the best idea would be to rent a car in Athens Airport or to hire a car in Piraeus Port. Prices are very competitive especially in the low season and if you do a market search you can find various special offers. Imperial Car Rental Athens hire cars with prices as low as 12 euro per day without any hidden extras or a requirement for a credit card deposit.
The road to Nafplio is actually a highway, almost a 2hours drive from Athens. There are a couple of tolls that might increase your total cost, but i think renting a car will still be the best value-for-money option.