Cruise ships typically dock right on Frenchman Bay at the Town Pier, located right in the town of Bar Harbor. Passengers are usually given a full day (8am to 8pm) to explore the area. Here is a suggested itinerary for how to explore Bar Harbor and Acadia National Park in under 12 hours.
Acadia National Park via Bus
From the Village Green (a 5 min walk from the pier), catch the #1 (Campgrounds) bus line to the Hulls Cover Visitor Center and get a map and some information from a park ranger. To explore the park, catch the #4 (Loop Road) bus and stop at Cadillac Mountain if you are up for a hike or Sieur de Monts, where you can enjoy a wonderful interpretive trail and beautiful gardens. A new bus will be by to pick you up 30 min after it drops you off at each location. Continue on to Sand Beach, which is lovely on a sunny day and then Jordan Pond for lunch and a stroll along a nature path. The bus takes a little over an hour to make the entire loop, but plan on at least a few hours if you are making multiple stops.
Oli's Trolley is a fun way to explore the park with a guide. This 2.5 hour tour is great if you want to sit back, relax, and learn. More info.
Bike Riding on the Carriage Roads
Bike Rentals: Start walking west on Cottage Street and you'll run into two bike shops (Acadia Bike 800-526-8615 and Bar Harbor Bike 207-288-3886) Both shops offer a variety of rentals, great for exploring the park carriage roads. Ask the shop for a map of the Carriage Roads.
Take the Bus: Once you have your bike, head on over to the Village Green (corner of Main St and Mount Desert St). This is the primary bus stop for the FREE Island Explorer which heads into Acadia National Park and all buses have bike racks. Pick up Bus 6 (Brown Mountain) and get off at the Brown Mountain/Gate House stop.
Ride to Jordan Pond: Ride the Carriage Road to Jordan Pond House, about 3 miles one way. Lock up your bike and have lunch.
Back to Town: The buses that leave Jordan Pond House are usually very busy and chances of finding a spot for your bike are slim. If there is a long line for the bus, hop back on your bike and either pedal back to the Gate House or head north to Eagle Lake. From Gate House, ride the #6 bus back to town. From Eagle Lake, ride the Bicycle Express bus back. Return your bike.
Things to Do in Bar Harbor
Abbe Museum: Just next to the Village Green, the Abbe Museum is an interesting stop if you are killing some time.
Art Galleries: Stroll through town and stop at art galleries and unique shops to peruse.
Brewery: Stop by Bar Harbor Brewing and sample one of their many micro-brews.
If you haven't had breakfast, head on down Cottage Street almost to Eden Street (it's a half mile walk or you can take a taxi). You'll see a restaurant called 2 Cats (207-288-2808) on the left. It's ranked #1 on TripAdvisor and offers an awesome assortment of big breakys and sweets. Grab a spot on the patio!
Lunch at Jordan Pond House
This is a great tradition in Acadia National Park. The Jordan Pond House (207-276-3316) opens at 11:30am for lunch. Stop in the restaurant first to see if there is a wait for a table. If there is a wait or if you aren't quite hungry, stroll along the 1-mile Jordan Pond Nature Trail. To get to the Jordan Pond House, take the Island Explorer Bus Line along the Loop Road.
Finish the day off with a dinner out at Galyn's ($$, 17 Main St), Side Street Café ($, 49 Rodick St), or Mache Bistro ($$, 135 Cottage St).