Lobster Pound Restaurant on Rt 1 in Lincolnville, ME is an excellent / quite popular choice for all types of seafood (and non seafood as well). They have a take-out setup for smaller items to have at their picnic tables near the water.
Moody’s diner in Waldoboro is a nice treat for breakfast, lunch or an informal supper.
Red’s in Wiscasset has an excellent lobster roll, but for the best lobster, clams, scallops, fish & chips, etc – it’s going to be hard to beat Five Islands Lobster Co in Georgetown, south of Bath. It has the freshest seafood where you eat on picnic tables along the wharf, overlooking some of the best scenery in ME. (Be sure there’s good weather as it’s all outdoor seating.)