Maine in the fall
 

We would like to rent a cottage or stay at a bed and breakfast where would could sit out in the evening and watch the ocean. We will be flying into Portland and renting a car. We will be all along the coast so if anyone has a suggestion. Also looking for must see spots and attractions. Thanks

I don't know a specific place, though I have spent a fair amount of time in Acadia/Bar Harbor, but I think in the fall you might hear the ocean, but you are unlikely to see anything but dark/black.

I live in Maine. There are many cottages and B & Bs where you could spend some time along the coast. And it's a long coast.

You didn't say how long you'd be staying. So, since you're flying in/out of Portland, take at look at these areas....
South of Portland....Kennebunkport, Ogunquit, York...all with beautiful beaches, accommodations and cottages, scenic walks, restaurants, etc. Wells, too....plenty of lodging, but without a "downtown". In Wells, everything is on or right off Route 1.
North of Portland....Boothbay Harbor, Camden, Rockport, and all the little inlets and coves along the way.
Acadia National Park/Mt. Desert....about 2.5 hrs from Portland. Worth an entire trip. Plenty of places to stay, lots to do. Gorgeous.
If you plan to go this fall....get busy....it's foliage season, and is almost as busy as summer.
Look at AcadiaMagic.com for accommodation suggestions, or VRBO, or there are rental agencies that also do cottage rentals along the coast.

High Tide Inn near Camden
Glenmoor-by-the-sea near Camden
Beloins near Camden
Ledges-by-the-Bay near Camden
or if you prefer sandy beach...……...Billowhouse in Ocean Park.

Note that first 12 or so days of October are mostly sold-out in Maine due to leaf-peeping. Book soon.