On the Water
The mailboat runs 6 miles from Stonington Harbor to Isle au Haut — about 45 minutes each way. Two stops: the Town Landing (year-round) and Duck Harbor in Acadia National Park (mid-June through early September). You get off the boat. There's a bathroom on board and a small waiting area at the dock. The casual version is the 10am mailboat to the Town Landing, walk around for an hour, ride back. The real version is Duck Harbor — take the 10am, arrive around 11:15, hike 4 hours of trails through coastal forest and ledge with almost nobody else around, catch the 4:45pm boat back, in Stonington by 6:15. That's roughly 8 hours door to door. No reservations — first-come, first-served, and the boat fills up in summer.
Insider Tip
Bring your own lunch and water. The island grocery store is a 5-mile hike from Duck Harbor with limited hours — don't count on it. And don't cut it close on the return ferry. There isn't a later one.
Time Needed
Full day (8 hrs for Duck Harbor) or 2–3 hrs Town Landing round trip
Weather
Clear or mild days only
Tide
Not a factor, but check the ferry schedule
Kid-Friendly
Town Landing for families, Duck Harbor for patient outdoorsy kids only