The A

U by Uniworld’s millennial-focused cruises nixed a 21-to-45 age limit, but they’re still a far cry from sedate river tours of old. U’s black-hulled ship, simply called A, officially debuted in April, sailing on the Rhine, Main and Danube rivers. It’s “part boutique hotel, part yacht, part local hot spot,” the company says. Replete with photo booth and farm-to-table cuisine, A docks at hip European cities for fun day excursions. —Joseph Hincks