The New Meadows River is beautiful body of water to explore. The Basin is one of the best hurricane holes in the Northeast and is very popular with coastal cruisers. We have spent many nights there on the hook, usually in 8-12ft of water. The bottom is mostly mud and the holding is good. You need to watch your depthfinder carefully once inside as there are some large rocks near the center. Some nights it is so still you'll think you went aground. On nights when there is little breeze the bugs can be murder.
A really nice place nearby is Sebasco Harbor Resort. You can get a mooring ($25) and have full use of their facilities; saltwater pool, reastaurants, ice cream shop plus gas, water and ice. You can even bring your golf clubs if you are so inclined.
To get to Boothbay from New Meadows you need to go around Cape Small past Seguin Light and either go up the Sheepscott then through Townsend Gut or if really adventurous, go up the Kennebec River to Bath then through upper and lower Hell's Gate, what a ride on an ebb tide!