I realize this is very subjective.
We've traveled to Europe many times but have not visited Greece or Turkey.
At the beginning of August we have the opportunity to take a small (50 cabin) upscale ship from Istanbul to Athens at a very good price. I know the weather will be hot and the crowds, heavy.
We could do this on our own, but frankly, I think the cruise will be far more cost effective.
We'd plan 5 nights in Istanbul at the onset and haven't figured out the end of the trip yet.
Is this a reasonable way to get a vague feel for the Greek Islands while remaining a little bit cooler on the water?
Thanks for any help!

A small cruise ship could be very pleasant, especially if it is one that spends a full day at each island on its itinerary, rather than 3-4 rushed hours. I gather that this upscale ship would be stopping at various islands en route to Athens.

If you would give the itinerary we could give you a better assessment. "A vague Feel" is a good way to describe the impression you probably would get of most islands, when you cannot spend time actually staying on an isle, but at least a smaller ship would allow you to have dinner ashore, and could go into smaller less totally-touricized ports. The Huge Biggie Cruise Ships can only go into 5 ports that are deep enough .... Mykonos, Patmos, Rhodes, Santorini, and Heraklion Crete... that is why they ballyhoo these destinations so heavily, they can't go anywhere else.

On the way from Istanbul a small ship could visit islands in the northeast Aegean like Samos, Ikaria, Lesvos... and then then in the Cyclades group, stop at isles like Naxos, Paros, Amorgos, Milos, Serifos, Syros and Kea.

Thanks so much for your response.
The smaller ports the cruise touches on are Molyvos, Naousa and Sifnos as well as Mykonos and Santorini.
Of course I'm aware that this would be far from in depth.
Alternatively we could just fly and ferry. I guess the heat and crowds in August make me feel that being on the water (and this ship has a "marina" with water toys) might be advantageous.

If you haven't cruised before, beware: cruising can become an addiction

Traveling in Greece is not expensive;the prices we paid were much less than for other European countries we have visited. I would have felt cheater if I had been on a ship.

Well, that's something I hadn't considered.
I've been concerned that I'd reach an island I wouldn't want to leave and I'd jump ship!

If the ship stays in port during the night hours, then I think it's a good option. By night hours I mean that perhaps it sails at midnight, as opposed to sailing at 5 pm.

The nightlife is one of the main reasons for traveling to Europe, in my opinion. You don't want to spend your evenings out at sea.

Such a small, luxury ship sounds like an opportunity that you shouldn't pass up. Yes, doing it on your own in Greece is easy, but it is high season and will be desperately hot. Being at sea sounds great--go for it!

We were told by many locals such as taxi drivers and guides at historical sites. That they won't have anything to do with cruise ship passengers. Just a heads up.The large ships have spoiled it for all the small ships. You'll be on a small ship but how many large ships will be in port the same day ruining it for you?

There are a couple of interesting things that Happytrvlr has mentioned that I'd like to address.
How do the locals know the tourists staying on island from those there from a cruise ship? I wouldn't sport any particular clothing to announce myself.
Certainly the large cruise ships in port would make for a less pleasant experience but I think this would be the case whether staying for a few days on the island or just one day.
Am I missing something?
That said, I think we are leaning toward Italy again as we've done that in the sweltering heat and crowds of August and survived!
I'll begin another Italy specific post, but there is much we haven't seen there and the cruise ship crowds are less than appealing in Greece.

They can tell the cruisers by when they arrive and how so many of them travel in groups.