Traveling the world without having to pack and unpack multiple times is ideal. Some ships have single cabins, host parties for single passengers, or even waive the single supplement fee river cruises tend to do that most often. But while a millennial might be looking to country hop around Europe or take a mixology class, someone who is in their 50s may be looking for a slightly different experience. Why you should sign up: Norwegian Sky was refurbished in and offers 10 dining options, a full-service Starbucks on board, and a casino for late-night bonding around the blackjack table with your new shipmates. Why you should sign up: This cruise line was originally built to cater to millennials, McDaniel said. The cruise includes excursions like a walking tour of Vienna and a palace tour.