The Great Lakes, which hold 21% of the world's surface fresh water and define regional identities, are now offering unique ways to explore them. Four cruises focusing on access and immersion allow guests to engage in research roles, explore industrial history, and explore ports that larger ships cannot reach. Viking's Great Lakes itineraries offer eight-to-17-day journeys where guests join scientists for ongoing environmental research. American Cruise Lines' domestic-only itineraries sail aboard American Patriot, a 130-guest small ship designed specifically for U.S. cruising. The Explorer-class cruise company offers a different approach to the Great Lakes.