This article is part of our latest special report on Waterfront Homes.
Every generation has had its own fixation with the deep, expressed in film, book or television: “20,000 Leagues Under the Sea” by Jules Verne; “The Undersea World of Jacques Cousteau”; Disney’s “The Little Mermaid”; and “SpongeBob SquarePants,” to name just a few.
Beneath the waves lies a place of mystery and adventure well beyond a run-of-the-mill existence. As Verne once wrote, “The sea is only the embodiment of a supernatural and wonderful existence.”
But now, thanks to advances in underwater construction and plucky entrepreneurs, it is possible to spend the night (or at least several hours) inside underwater hotels, restaurants and even homes.
Undersea offerings range from no-frills base stations for scuba enthusiasts to five-star private villas. Some revel in the dazzle of being underwater, others accentuate ocean habitats and a few even contain scientific facilities for researchers.
Captain Nemo would approve. Experience-obsessed travelers and social media influencers already do.
Located along the southernmost tip of the Norwegian coastline — where the dark waters of the North Sea meet the tranquil, clearer ones of the Baltic Sea — Under is one of the world’s most unique restaurants. Half-sunk into the sea, the 34-foot-long concrete and wood building — resembling a high-concept subway car — features a 36-foot-wide acrylic window that offers views of the craggy seabed, its remarkably varied plant and animal life, and the area’s notoriously erratic weather.
In contrast with the mercurial conditions and industrial exterior, visitors pass through an intimate wood- and fabric-clad entrance and progress down into a cavernous dining room, where surfaces become more minimalist and the ocean casts its greenish-blue glow over everything.
“There’s a directness, an honesty to the project,” said Craig Dykers, a principal at Snohetta, the architecture firm that designed Under. He noted that all the materials used in the project were natural and that nothing was hidden behind a false surface.
The seasonal menu, too, is unadorned. The food is clearly presented, not refashioned or smothered in sauces. There is one exception to Under’s spare presentation: Warm spotlights illuminate the food, so the same greenish-blue tint that pervades the room doesn’t lessen the appeal of the dishes.
Under, which was craned into place by a team specializing in underwater infrastructure, is more than a restaurant: It also serves as a marine station for the Norwegian Institute of Bioeconomy Research, with cameras and sensors installed along its facade. Thanks to careful planning, which included habitat cleanup and the reintroduction of long-departed sea life, the building’s shell has become an artificial reef, covered with a dense jungle of dark-green kelp and algae, and teeming with other marine life.
Jules’ Undersea Lodge
Starting its life in 1971 as La Chalupa, an underwater research laboratory off the coast of Puerto Rico, Jules’ Undersea Lodge was transported to its protected lagoon home in Key Largo, Fla., in 1985 by the marine scientist Ian Koblick, who later transformed it into a hotel. The building sits on stilts about five feet off the lagoon floor, and it may be the only hotel in the world that requires you to scuba dive to enter.
“It’s only second to going to space,” Mr. Koblick said of staying at the hotel. He set it up to share the surreal moments he had experienced as a researcher and to raise awareness of marine protection.
The hotel is basically an underwater trailer. A 1,700-square-foot living area includes a common room, two bedrooms, a bathroom and a wet room for divers to arrive and depart. There is a 42-inch-round window from which the diverse sea life can be seen passing by, and guests can head out whenever they like (with or without a guide, depending on experience level) to explore the lagoon to see mangrove snapper, grouper, angel fish, spade fish and even barracuda, sea horses and manatee. There are also the remains of a sunken 19th-century ship that can be explored, including cannons and the anchor. Guests are monitored for safety 24/7 by staff members, and food is delivered and served by a diving “mer-chef,” as the lodge’s site calls it. Guests can even order pizza.
The experience has drawn celebrities such as the Aerosmith singer Steven Tyler and Jacques Cousteau’s son Jean-Michel, a film producer and conservationist, Mr. Koblick said. Recently, social media influencers have started visiting, including video bloggers like Mark Vins and Safiya Nygaard.
In addition to the hotel, the facility offers scuba training and certification, while its MarineLab underwater research and education habitat is a base for Mr. Koblick’s Marine Resources Development Foundation, which promotes responsible and sustainable use of marine resources through classes and research.
Conrad Maldives Rangali Island
Located about 60 miles from Malé, the island capital of the Maldives, in the South Ari Atoll, Conrad Maldives Rangali Island resort is reachable via seaplane or speedboat. Visitors who complete the journey can visit the Ithaa Undersea Restaurant and the Muraka, a villa whose main bedroom is submerged beneath the Indian Ocean.
“When you only have access to life above the surface, you’re missing 50 percent of what makes the destination so magical,” said Carla Puverel, the resort’s general manager.
About 16 feet below the water’s surface, Ithaa (which translates to “pearl” in the Maldivian language of Divehi) is wrapped in a half cylinder of acrylic, enveloping diners in coral gardens and colorful tropical fish, not to mention the occasional sharks, stingrays and turtles. Its original design, Ms. Puverel said, was box-shaped. But the Maldivian architect Ahmed Saleem lobbied to shift to a curved shape for a more panoramic experience. He received engineering assistance from Mike Murphy, an aquarium technology specialist from New Zealand.
After Ithaa’s success, the resort again chose Mr. Saleem and Mr. Murphy for the Muraka. (Interiors were designed by the Japanese architect Yuji Yamazaki). Its top floor, which resembles a midcentury modern home floating in the ocean, includes two bedrooms, a large living room and an outdoor deck with an infinity pool. Downstairs, the main bedroom is wrapped with a curved acrylic ceiling, similar to Ithaa’s. Even the bathroom, shower and closets are surrounded by ocean life via floor-to-ceiling windows. For an even more immersive experience, there is a panoramic viewing room at the end of a tunnel-shaped bedroom. Each piece of the 600-ton lower level was constructed in Singapore and transported to the Maldives before being secured underwater with concrete pilings. At night, lights embedded in the rocks illuminate schools of fish swimming by.
Elsewhere in the Maldives, visitors willing to take a seaplane can check out Subsix, an underwater nightclub and restaurant off the coast of the Niyama Resort, which is on two private islands (somewhat comically named Play and Chill) in the Dhaalu Atoll. Guests descend three stories to a surreal space with floor-to-ceiling windows and a chandelier of hanging, translucent disks that evokes a coral reef. There is a clam-shaped bar and spiky black “urchin” chairs.
The World is a manufactured (and somewhat troubled) archipelago off the coast of Dubai consisting of over 200 islands representing countries around the globe. The Heart of Europe is a development within that development, inspired by countries, cities and regions like Germany, Sweden, Switzerland, the Côte d’Azur and Venice. Within this mix are the 4,000-square-foot, 400-ton Seahorse Villas, which are floating homes built partly underwater and developed by the Dubai-based Kleindienst Group.
Above water in each villa are two levels of window-wrapped indoor spaces, including bedrooms, a kitchen and a living room, as well as a large patio, and alfresco dining and balcony spaces — fitted with furniture, hot tubs and outdoor showers — affording views of Dubai’s skyline. The downstairs offers concrete-framed bedrooms that are fitted with floor-to-ceiling, four-inch-thick acrylic windows that look out at aqua-blue waters and tropical fish, which are attracted to coral that has been attached to the structures.