Directions: From Route 3, bear right onto Route 102 toward Southwest Harbor. After passing through Southwest Harbor, stay on Route 102. Take a left onto Bernard Road. Turn right onto Lopaus Point Road. Look for a little parking area on the left. You should be able to see Back Beach through a small patch of trees. There will be a house off to the right of the opening through the trees.
Paddling Information: Back Beach is not one of the more common launching areas. Located in Bass Harbor, it's a little out of the way. It may be a little hard to locate. The beach is a boulder beach as most are on the island. It's fairly isolated in that area. It is not a heavily used launching spot. From Bass Harbor, I recommend paddling north along the western side of Mt. Desert. That's a right as you are leaving the harbor. It is tempting to head in the other direction toward the Bass Harbor Lighthouse, but that brings you into more open ocean, and at times there are strong currents in the area near the lighthouse.
You can also head up into the harbor, and paddle in the tidal marshes. However, you must watch the tides or it will be difficult to get in and out of the marshes. Sorry, I have not done this, so I cannot advise you on the timing. Ask some of the locals for advice.