Why didn't I think of Windjammer?!?!?!?!?!
I know this doesn't answer your original question, but it sounds like Windjammer cruises might be a perfect fit for you. They are not "normal" cruises. My mom took one of their Tahiti cruises ten years ago and still talks about it. (She is ULTRA-sensitive to anything remotely CHEESY......This was not!!!) There was about a 1-1 guest to staff ratio (small boat, only 85 guests), they dove and snorkeled off of the back of the boat, were taken on tours of the local areas, the food was incredible.....and none of the cheesy shows or bingo nights that you get on a "normal" cruise. In fact, almost everyone was asleep by 10:00 because of how tired they were. There was very little actual "crusing" on open water...so there was lots of "lazy" beach time too.
Take a look!!!!
Also, for all of the future doctors.....four of the guest slots on her cruise were taken up by a doctor, his wife, their 11 year old and her best friend...all compliments of the cruise line! (Keep your eye on all of those doctor perks!!!)