Misty Harbor near Meadowbrook are under $100K. They are converted hotel rooms. I don't know about moorings but they have an indoor pool and a nice beach.
Goto
www.nneren.com and you can search by town for condos under 100K.
We owned a place at Samoset for a few years, they have mooring and dock but are well over $200K. Mineral springs across the street are between $100 and 200K and have access to moorings.