Seeking input on Greece itinerary

Hydra was not a part of our visit to Greece, so I am unable to advise you on that part. We chose to fly from Naxos to Athens, and found that to be a very efficient use of our time. We encountered a one day ferry strike while in Greece, so if you do choose to go that route, have a back-up plan in mind...just in case. The ferry company never informed us of the strike. We had enrolled in STEP, before leaving the U.S., and they sent us an alert.

Day 12: Take morning ferry to Athens

You really want to spend 5+ hrs on a boat vs. a 40 minute flight?

If you have planned out your time in Athens and get to everything you want in 2 days plus the bit of the day you sail, then do it. Otherwise flying may deserve consideration.

Good points! Thank you — I appreciate your insight. : )

Regarding Day 12, I agree with Joe's comment about the Naxos → Athens part, but you shouldn't just consider the ferry vs. flight travel time.

From Naxos, the first flights to Athens are around noon, which means you'll land around 12:30/1:00 PM and arrive in downtown Athens about 90 minutes later (no earlier than 2:00 PM in the best case scenario).

Furthermore, you should also consider that, as I assume you'll be staying near Naxos Town, you'll need to arrange a transfer from the hotel to the airport at least 90 minutes before the flight, i.e., around 10:30 AM.
You won't have to arrange this transfer if you take a ferry.

The first ferry to Piraeus is at 9:30 AM, arriving at Piraeus at 3:30 PM. You'll be in downtown Athens about 30 minutes later (let's say at 4 pm).
The difference between the ferry and the flight is only 2 hours at most.

Also, check the availability of Naxos → Athens morning flights in May, some are already sold out unless you take the high fare (around €150 per passenger). The ferry trip costs €52 per passenger.

Day 4: Hydra → Ermioni:

There are no departures to Ermioni before 8 pm with traditional ferries. Check with "Hydra Tour Travel." It's a small local boat with departures every day at 8:30 am, 11 am, and 3 pm.

https://www.hydratourstravel.gr/index_en.html

To my knowledge, the only car rental company in Ermioni that allows you to return your car in Athens is Pop's Car.

https://popscar.gr/

There will be a fee of €40 to €45 (depending on the type of car) for returning the car to Athens airport.

Picking a couple random dates in May, I find Olympic Air has a flight leaving Naxos at 10:05 AM with a scheduled arrival at 10:55 AM.

Using JoLui's timing of 90 minutes to central Athens has you there around 12:30. vs the boat's 4PM

Fly or sail, up to you; just be sure to research your options to make an informed choice

You'll have to decide quickly for the 10:05 Olympic flight; there aren't many options left:

2 seats on May 13

A few seats on May 14

4 seats on May 15

2 seats on May 18

A few seats on May 20

3 seats on May 26

Other days are sold out or with only 1 seat available. :((

Thank you so much for these replies! I didn’t see them until now, but I do appreciate your advice and information! I may have to modify our plans based on limited flight availability / time constraints…. I will try to figure things out asap! Thank you again!!!!