The river is great for swimming, but never swim alone or during high water. There are no life-guarded swimming areas. Diving is extremely dangerous because of unseen rocks and logs beneath the water's surface. Glass containers are prohibited on the river, on trails, within 50 feet of any stream or river bank, and in caves.
Maine ocean islands provide the only nesting sites for Atlantic puffins in the United States. Eastern Egg Rock in the midcoast region, Seal Island and Matinicus Rock at the mouth of Penobscot Bay, and Machias Seal Island and Petit Manan Island off the downeast coast provide habitat for more than 4,000 puffins each summer.