Just about as far Down East as can be, you can paddle past a ship sunk for two centuries, and cliffs carved for far longer. Mysterious petroglyphs crafted long ago near the modern-day home of the Passamaquoddy may not last for long, as water levels rise and winter ice takes a toll on the ancient etchings. ‘‘They’re going to be lost, probably in the next 10 years, from erosion,’’ said Jen Scribner, of Sunrise Canoe and Kayak. ‘‘They’re definitely taking a beating in winter.’’ Sunrise Canoe and Kayak, 68 Hoyttown Road, Machias, 877-980-2300, www.sunrisecanoeandkayak.com.