We recently spent 5 nights on the Narnie O'Shea and it was a wonderful experience. I am so happy I found it here on tripadvisor. Chalium was a great host and the yacht and marina were just as the wesbite photo's show - awesome. While it is fun to stay on a yacht, the hotel and marina ammenities really make it comfortable, especially if you are on the taller side!
Shelter Island is a great place to stay, close by to everything with free parking for those with a car, and places to eat and drink in easy walking distance. We would come back in a heartbeat.