"Great Adventures" Greek Isles Tours?

My wife and I have always viewed "cruising" as a sampler platter against future visits. We really enjoyed the stops in Santorini and Mykonos on a recent Celebrity cruise, so we've been considering a more in-depth "Greek Isles" cruise.

We really liked the look and feel of this Great Adventures' Greek Isles yacht tours:

http://www.gadventures.com/marine/greek-islands-sailing/

Has anyone done such a thing before? Tiny little 10-passenger ship, it barely qualifies as "Cruising" (and so this might even be considered off-topic), but it seems FASCINATING, and I was just trying to see if anyone had practical experience with them in the past?

I guess they're actually called "G Adventures" (formerly Gap Adventures, until GAP Clothing had an issue with that).

G Adventures has an expedition ship (called Expedition) which goes to the Antarctic and Arctic. We went to the Antarctic in 2015 on Expedition which has about 130 passengers. It was a very well run trip in every way. G Adventures runs many land tours as well.