It's probably the DuoLingo World Cruise thing: https://www.carnival.com/duolingo

The "prank" itself is just regular corporate PR noise, but there's some gems in there, and I think the HN crowd would appreciate the terms and conditions at the very bottom:

Passengers also waive the right to pursue legal action against Carnival or Duolingo, including participation in any class-action lawsuits filed by Menchetti & Sons LLC., a law firm with a history of unfounded litigation against companies providing “transformative” experiences. Any legal concerns will be handled exclusively by Legal Steve, Duolingo’s Chief of Legal Counsel, who has pioneered the “litigation loop” strategy, ensuring that all claims are met with immediate counterclaims until the original complaint is forgotten.