The mile-long hike up the blueberry-covered Blue Hill Mountain lifts you almost 1,000 feet in just an hour or two of hiking. From the fire tower on the summit, a stunning panorama takes in Acadia , the Penobscot Bay  islands, and the Camden Hills. The trailhead is located on Mountain Road, off Route 15.
Deer Isle  has several short hikes to quiet coves, mud flats, and tidal pools, where it’s not unusual to spot nesting eagles and osprey. A trail map is available from the Island Heritage Trust (3 Main St., 207/348-2455, www.islandheritagetrust.org ), which manages the preserves.
The rocky coves of the peninsula are ready-made for kayaking. Castine Kayak Adventures (17 Sea St., 207/866-3506, www.castinekayak.com ) offers kayak rentals ($45–60/day), guided tours, moonlight paddles, and overnight trips, including expeditions in search of stunning phosphorescent plankton. Boats leave from the Dennett’s Wharf in Castine Harbor.
Educational nature cruises around Blue Hill Bay and Eggemoggin Reach are offered by the scientists of the Marine Environmental Research Institute (www.meriresearch.org , 207/374-2135). Suitable for both children and adults, the three- and four-hour trips go in search of seals, seabirds, eagles, and porpoises.