Exterior shot of The B in Paris at night

(3:10 p.m. EST) -- Slated to launch in April as the first cruise line aimed at millennials, new river cruise line U by Uniworld is already abandoning its original age limits and opening all of its sailings to all adult cruisers.

Originally, U by Uniworld set itself up as a cruise line meant solely for travelers ages 21 to 45. An offshoot of the luxury river cruise line Uniworld, U by Uniworld stressed a youthful vibe, with activities such as rooftop excursions of Paris, silent discos, craft cocktails and other millennial-focused offerings. The line's two 120-passenger ships, The A and The B, were revamped in modern decor, including cabins that were meant for friends bunking together, and spaces that focused on hanging out, such as communal dining tables and a lounge on the top deck.

Opening the sailings to adult travelers of all ages will not change the way the cruise line operates, a spokesperson said.

"Originally, U was very specific in defining its target market, but has learned that the experience is less about a number and more about attracting a new generation of adult travelers to river cruising," said spokesperson Devyn Barker, in an email. "U by Uniworld will remain the same with sexy, stylish ships and itineraries that focus on longer stays in destination, allowing guests to connect with local people and experiences and each city's vibrant nightlife.

"Removing the gated age restriction will not change the product or our efforts to attract a new generation of adult travelers."

The ship's itineraries on the Seine, the Rhine, the Main and the Danube have not changed from their original launch; however, the age restrictions have been removed from the company website.

U by Uniworld isn't the only river cruise line to reach out to millennials. Amadeus, a European river cruise line, has planned millennial sailings in 2019, featuring five- and six-night voyages on the Rhine, Rhone and Danube. Cruises are focused on celebrity influencers, who are onboard each sailing to serve as hosts while documenting the experience for their social media followers.

The change in U by Uniworld's booking policies, however, casts doubt on whether millennials can fill an entire river cruise ship.

For more on what U by Uniworld has to offer, check out a photo gallery of The B). The A was recently featured on the ABC TV show "The Bachelor."

--By Chris Gray Faust, Managing Editor