Cruise companies have been obsessed with firsts, as of late.

Last year, Royal Caribbean debuted the world’s largest ship, Harmony of the Seas, while Regent Seven Seas Cruises launched the $450-million Seven Seas Explorer, the most expensive ship ever built.

And now, the French expedition cruise company Ponant is getting in on the game by launching the first-ever underwater lounge at sea. Blue Eye, a sleek, multi-sensory space, will be unveiled on the brand’s four new Ponant Explorers: Le Bougainville, Le Dumont-d'Urville, Le Lapérouse and Le Champlain.

On board each ship, passengers will be able to head beneath the water line to the Blue Eye lounge. There are two large glass portholes designed like the eyes of a whale that let passengers peer out into the depths below, digital screens that project live images filmed by three underwater cameras, marine surround-sound based on sounds in within a three-mile radius of the ship, and sofas that vibrate in unison with the sea.

The four yachts, which will be rolled out in 2018 and 2019, should prove to be popular, as the desire for expedition cruising — a method of travel that highlights small, hard-to-reach ports, immersive wildlife excursions, and on-board experts and naturalists — only continues to grow.

Other companies set to unveil next-gen expedition vessels include Silversea, which will refit the Silver Cloud to focus on polar sailings; Norwegian-line Hurtigruten; and Scenic, with its ultra-luxury expedition yacht, the Scenic Eclipse.