I agree with previous posts. One that hasn't been mentioned is the Maine Transportation Museum. All types of transportation. cars, planes, motorcycles, bikes, steam, engine display and more.
Don't know how interesting you would think it is, but the "Old Sow" is one of the biggest whirl pools. Its north east of bar harbor clear at the top of the coast line. Every 6 hours the tide raises and falls about 20ft.
https://www.google.com/search?q=old+sow+whirlpool+map&rlz=1C1GGGE_enUS602US602&oq=ols+sow+ma&aqs=chrome.2.69i57j0l4.7373j1j8&sourceid=chrome&ie=UTF-8
