Harmony of the Seas

Harmony of the Seas restarted the Oasis class after a six-year gap and moved its construction from Finland to Saint-Nazaire — the same slipways that built the France, the Queen Mary 2's hull sections, and, forty years earlier, the largest supertankers ever floated. At delivery in May 2016 she was the largest cruise ship yet built, at 226,963 gross tons.

She introduced the Ultimate Abyss, a ten-storey dry slide dropping from the top of the aft towers, and the class's third generation of energy systems — air lubrication under the hull and a heat-recovery plant that cut fuel burn noticeably against her older sisters.

Two years later her own sister Symphony took the title, which is simply how the Oasis class operated for a decade and a half: the record never left the family, it just moved one hull along.