General view during the delivery ceremony of the Harmony of the Seas (Oasis 3) class ship at the STX Les Chantiers de l'Atlantique shipyard site in Saint-Nazaire, France, May 12, 2016. [Photo/Agencies]

Among the onboard attractions are "The Ultimate Abyss", a 10-story slide from the top deck to the main deck which RCCL bills as the world's biggest ship-mounted waterslide.

A giant climbing wall, a rope slide, mini-golf, surf simulator, floating jacuzzis, a casino and 1,400-seat theater playing Broadway musicals are among the other attractions.

Two robot barmen will serve passengers in the "Bionic Bar".

The ship even has its own high street, and a "Central Park" deck featuring 12,000 plant species.