When the weather's hot, what could be better than plunging into a clear, cool lake, river, or pond? Whether you're swimming in the saltwater of Acadia's coastal waters, the seven sacred pools of Oheo Gulch in Haleakala National Park, or the icey cold lakes in Glacier National Park, swimming is a great way to cool-off, relax, and have some good old-fashioned fun in the parks. Locations are widely available in many parks, just remember to find out about local rules and regulations and designated swimming areas before your visit.