The first of its kind, the hotel group introduces luxury design at sea

On Deck 5, the turquoise pool does double duty: During the day, it's a place to lounge with a cocktail; at night, the entire pool can be emptied and the floor raises so that the area can host private events.

When the Four Seasons I set sail on its maiden voyage off the coast of Málaga, Spain, in March, the ship—from the newly launched Four Seasons Yachts—had all the markings of a luxury hotel at sea. But everyone involved in the project, from Four Seasons Yachts CEO Ben Trodd to creative director Prosper Assouline, is careful not to use the “c” word: cruise. This is a yacht. In fact, it’s a 679-foot superyacht.

The 679-foot Four Seasons 1 set sail off the coast of Málaga, Spain, in March.

The specificity makes sense—when was the last time a cruise ship could boast an average guest room size of 581 square feet? Or a bar with églomisé cocktail tables, each one crafted in London and commissioned by AD100 firm MBDS ?…