Snohetta
Under, Europe's first underwater restaurant, is now open in the small town of Båly, overlooking the Skagerrak strait, in the southernmost area of Norway.
Snohetta
The entrance is at shore level, and the area where the restaurant is submerged is often battered by severe weather -- which makes for a more spectacular underwater view, according to the architects.
Snohetta
The 110-foot long structure, an oblique concrete slab that looks like a sunken periscope, was submerged in July 2018 and opened to the public on March 20.
Snohetta
"Under is a natural progression of our experimentation with boundaries," Snøhetta founder, Kjetil Trædal Thorsen, said in a statement.
Snohetta
The restaurant was built in about six months on a barge near the coast, then towed into position -- about 600 feet away -- with a heavy-lift vessel.
Snohetta
The structure weighs 2,500 tons and is made of reinforced concrete.
Snohetta
A large, 36-foot wide acrylic glass window will offer underwater views to about 35-40 seating guests.
Snohetta
The structure is designed to withstand "a thousand-year wave," or an event of extraordinarily unusual force. The concrete walls are half a meter thick.
Aldo Amoretti
These images show the structure before it was laid down on the sea bed.
Aldo Amoretti
The total internal area is about 500 square meters (5,300 square ft) set over three levels.
Aldo Amoretti
Environmental considerations have informed the construction, and research groups will be welcome in the finished structure to study the surroundings.
Aldo Amoretti
Work has been done to restore the conditions that were in place prior to the disturbance created by submerging the structure, and the concrete shell is designed to invite mussels to cling onto it and blend into the surrounding nature.
Aldo Amoretti
The tasting menu, created by Danish head chef Nicolai Ellitsgaard Pedersen, relies heavily on local seafood, although mushrooms, berries, various seabirds and wild sheep from the surrounding landscape will also be on offer.
Aldo Amoretti
Interior lighting is muted and discreet to avoid such reflections, and colors are chosen accordingly, with oak wood and fabric covering the walls to avoid glaring white spots.
Aldo Amoretti
Norwegian outfit Snøhetta has made a name for itself with projects such as the Bibliotheca Alexandrina in Egypt, the Oslo Opera House, the National September 11 Memorial Pavilion and the renovation of Times Square in New York.
Kleindienst/Floating Seahorse
Other examples of underwater construction include, the Floating Seahorse villas that take the houseboat concept to the next level: each three-story retreat features an entire floor submerged beneath the sea. Brought to life by Kleindienst real estate and property developers, the villas are part of the Heart of Europe resort opening off the coast of Dubai.
Kleindienst
On the outside hull, the architects used three main components: Glass Reinforced Plastic (GRP), steel, and acrylic. Connecting the acrylic to the hull was another challenge, as it required a highly flexible, long-lasting sealant that only about three companies in the world make -- of those, only one supplier was able to match the project's technical requirements. 
Kleindienst/Sharbeen Sarash
Stretching across three levels, Floating Seahorse villas include two underwater bedrooms, an outdoor sun deck, and a rooftop with a glass-bottom Jacuzzi. Around 50 floating abodes will be ready to welcome guests at the end of this year, with a total of 131 villas expected by the end of 2017. 
Sharbeen Sarash
At just 9.5 centimeters thick, the floor-to-ceiling underwater windows make it seems like there's nothing between you and the fish. However they're not made of glass, as that would cause distortion and could not withstand the water pressure. Instead, the team looked to aquariums and submarines and used acrylic for its durability and crystal-clear views. 
Kleindienst
Inspired by the mysteries of the deep, Kleindienst studied underwater projects for decades until he finally had the chance to bring his vision to life in 2008, as part of the "The World" project off the coast of Dubai.
Dymitr Malcew
Another example is the Floating House, designed by Singapore-based architect Dymitr Malcew, which aims to make the nomad life as leisurely and luxurious as possible. Each home is fully sustainable, built with its own water purification system and solar panels for electricity.
Dymitr Malcew
When building The Floating House, one of architect Dymitr Malcew's main goals was to complement the surroundings. Taking inspiration from nature, the design accentuates the landscape, featuring floor-to-ceiling glass curtain walls and an abundance of wood. Each room has easy-access to a wrap-around terrace, and enormous windows let in lots of natural light.
Dymitr Malcew
To enable The Floating House to rise and fall with the tides, architect Dymitr Malcew constructed the home on floating steel pontoons. An engine can be installed upon request, enabling owners to travel the world from the comfort of their own home.
Architect Koen Olthuis - Waterstudio.NL/developer: ONW/BNG GO
Another ambitious project comes from Dutch developers ONW/BNG GO. The Citadel is Europe's first floating apartment building. It's part of the New Water development project, which will comprise six floating apartment buildings -- all designed to adapt to flooding and rising water levels.
Architect Koen Olthuis - Waterstudio.NL/developer: ONW/BNG GO
The Citadel floating apartment building is home to 180 modules, which rest on top of a floating concrete foundation. A floating road connects the complex to the shore, so residents can park their cars on site. Dutch developers ONW/BNG GO designed the complex to be highly efficient, consuming 25 percent less energy than a conventional building of the same size.
Robert Harvey Oshatz, architect / Cameron Neilson, photographer
Made with a mix of western red cedar, Douglas Fir and copper, the Randall T. Fennell Residence sits gracefully on the Willamette River in Portland, Oregon. Curving rooftops mimic the ripples in the water below and create an eye-catching silhouette.
Cameron R Neilson
The residence's exposed beams add an industrial feel, while curved ceilings and rich wood warm up the vibe. A deck wraps around the home, leading visitors to the open-air patio in the front of the home where they can take in dramatic sunset views.
Robert Harvey Oshatz, architect / Cameron Neilson, photographer
Surprisingly spacious inside, the 2,153-square-foot (200sqm) houseboat includes a loft-style master bedroom and an open living space. Drawn up like a sail, a clean white wall draws focus to the piece de resistance: a floor-to-ceiling glass window that looks onto the river.
Jose Campos Photography
This floating abode is all about sustainable, mobile living -- anywhere in the world. From the designers of Friday SA, a Portuguese design and engineering firm, Floatwing was built to travel and its modular design can be broken down and transported in two or three shipping containers. You can anchor where you wish, or motor around at a speed of up to 3 knots.
Jose Campos Photography
As stylish as it is sustainable, Floatwing homes come with a wine cellar, barbecue area and a rooftop terrace. As for sustainability, the designers chose eco-friendly materials such as cork and wood. It's energy efficient too, thanks to double-glazed panels for insulations and solar panels that cover up to 80 percent of energy consumption throughout the year.
MOS Architects / photographer Florian Holzherr
Tucked away in the Great Lakes, MOS Architects' one-bedroom Floating House rests atop steel pontoons, allowing it to rise and fall with water levels. Built off site, the house traveled about 50 miles before reaching its home on the remote island in Lake Huron.
MOS Architects / photographer Florian Holzherr
Inspired by the surroundings, MOS Architects designed Floating House Lake Huron with clean lines and a natural palette. Inside, bright white walls and enormous windows open up the ground floor's 1,000-square-foot space (92 square meters), while cedar rain screens on the facade offer both form and function.
Designs Northwest Architects / photographer Ben Benschneider
A project by Designs Northwest Architects, Lake Union Float Home is part of Seattle's unique houseboat community. Inspired by the century-old marina warehouses on the docks, the architects created a modern home with historical touches, evident in the industrial form, steel beams, polished concrete and caged spiral staircase.
Jet Capsule
Don't worry: these are not a figment of your imagination. Made of two fiberglass shells, the UFO (which in this case, stands for unidentified floating object) is essentially what it looks like -- a spherical boat, able to reach a top speed of 3-5 knots.
Jet Capsule
The shells are made of fiberglass and secured with a hermetic seal, which keep it afloat and stable. The Italian company behind the concept, Jet Capsule, says the sphere is unsinkable, utilizing a special elastic anchor system to maintain stability in rough seas.
Jet Capsule
The UFO is completely self-sustaining, incorporating innovative features like a water generator that turns salt water and rain into potable water. The mobile home also has solar panels and optional water turbines to power the battery. 
ewout huibers
Stretching across 2,152 square feet, Watervilla Weesperzijde sits on Amsterdam's Amstel River. Designed by +31ARCHITECTS, it's all about the river views: luxurious floating abode boasts a glass façade and a terrace that runs the entire length of the villa. Tech-savvy touches, such as automatic sun shades and strategically placed LED lights add a modern touch.
+31ARCHITECTS
House boats are nothing new in the Netherlands, where much of the land lies beneath sea level and is susceptible to flooding. Designed and constructed by +31ARCHITECTS, the 2,120-square-foot Watervilla de Omval floats on the Amstel River. It's a contemporary take on the traditional houseboat, featuring a curvaceous exterior, glass-front façade and a rooftop terrace to make the most of the surrounds.
BYTR/Stijnstijl photographer
You won't find any portholes aboard The ParkArk Oog-in-Al, but the contemporary houseboat still floods with natural light from enormous windows and skylights. Another custom project from BYTR architects, the copper-clad boat is moored on a leafy green canal in Utrecht right next to a footbridge. Due to its public location, the designers strategically planned the home's doors and windows to enable park and river views while maintaining a sense of privacy.
BYTR/Liesbeth Sluiter photographer
Designed and built by BYTR architects, Muntboot sits on a quiet canal in Utrecht, a city in the Netherlands that's known for its medieval waterways. The split-level houseboat could easily double as a piece of artwork, thanks to wooden slants of various widths that give the façade texture and depth.
CNN  — 

Five meters below the surface of the North Sea, near the southernmost tip of Norway, Europe’s first underwater restaurant is now complete. The 110-foot long structure, an oblique concrete slab that looks like a sunken periscope, was submerged in July 2018 and welcomed the first guests on March 20.

The restaurant, called Under, is the design of Norwegian outfit Snøhetta, which has made a name for itself with projects such as the Bibliotheca Alexandrina in Egypt, the Oslo Opera House, the National September 11 Memorial Pavilion and the renovation of Times Square in New York.

Under sits up to 40 guests, protected by concrete walls half a meter (1.6 feet) thick, and has a total internal area of about 500 square meters (5,300 square feet) set over three levels, offering unique underwater views of the surrounding marine environment through a 11-meter (36 feet) wide panoramic window.

“Under is a natural progression of our experimentation with boundaries,” Snøhetta founder, Kjetil Trædal Thorsen, said in a statement. “As a new landmark for Southern Norway, Under proposes unexpected combinations of pronouns and prepositions, and challenges what determines a person’s physical placement in their environment. In this building, you may find yourself under water, over the seabed, between land and sea. This will offer you new perspectives and ways of seeing the world, both beyond and beneath the waterline”.

How Under went under

The restaurant was built in about six months on a barge near the coast, then towed into position – about 600 feet away – with a heavy-lift vessel. To submerge the structure, containers filled with water were placed inside, before securing it to the sea floor with a total of 18 anchoring points.

Aldo Amoretti
Under when it was under construction.

“It was a delicate operation, as the clearance to meet the bolts was just two inches,” Rune Grasdal, a senior architect at Snøhetta, said in a phone interview.

More than half of the structure is submerged, and guests gain access through a glass walkway that will bridge the gap between the coast and the entrance, which is at shore level.

Under is made of reinforced concrete, to withstand the harsh conditions found in this spot of the Norwegian coastline. “The first problem is water pressure, as we’re five meters (16 feet) below the surface, but the biggest challenge is the waves. Wind and waves are extreme here. To withstand all these forces, the building is slightly curved, so it can better take to the waves, and it’s thick: half a meter (1.6 feet) for the concrete and about 30 centimeters (1 foot) for the acrylic windows,” said Grasdal.

Snohetta
The finished structure.

A simple design

The decision to position the restaurant in an area battered by the elements was deliberate. “When the client came to us, they had already done some sketches on another site close to current one, but we convinced them to build a few hundred meters away, where the sea is actually rougher. We thought this would better capture the nature of the area and I think that’s also what makes this more spectacular compared to other underwater restaurants in the world, as they are in very controlled areas,” said Grasdal.

The client, developers Gaute and Stig Ubostad, also operates a hotel a short distance from the restaurant. They both sit in the Lindesnes region, home to Norway’s oldest lighthouse, a popular tourist attraction located at the southernmost tip of of the mainland. Getting here isn’t too easy: the best way is to hop on a short flight from Oslo to Kristiansand, the closest airport, which is about an hour’s drive away. Grasdal said that a boat service is in the works.

The design of the structure was also subject to several revisions. “Initially, we spent a lot of time on very complicated designs, but after a long discussion and many different models we ended up doing things in a much simpler way. It’s just a concrete tube that brings people from the land down to the sea, it’s so simple. When we reached that conclusion, it was a actually relief,” said Grasdal.

Aldo Amoretti
A detail of the construction site.

A light touch

To guarantee the safety of the guests, an analysis has been performed to study the propagation and load of the waves, and the 2,500-ton structure is designed to withstand the most extreme events. The data will also be fed back to visiting research teams that study marine biology and fish behavior. Work has been done to restore the conditions that were in place prior to the disturbance created by submerging the structure, and the concrete shell is designed to invite mussels to cling onto it and blend into the surrounding nature.

The tasting menu, created by Danish head chef Nicolai Ellitsgaard Pedersen, relies heavily on local seafood, although mushrooms, berries, various seabirds and wild sheep from the surrounding landscape will also be on offer.

From the main window in the dining area, which is 4 meters (13 feet) tall, guests will be able to observe a variety of fish and sea creatures including seals and lobsters. Crucial to this view is the lighting, which has been carefully designed for both the interior and the sandbank just outside. “Outside lighting is very important because in the wintertime and in the evenings it will be dark, and without any light you would just see the reflection of the restaurant on the window,” said Grasdal.

Snohetta
Under from above.

Interior lighting is muted and discreet to avoid such reflections, and colors are chosen accordingly, with oak wood and fabric covering the walls to avoid glaring white spots.

“It’s a magic feeling to be down in a big room like this and see out into the sea through the huge window And what’s surprising is that some of the renderings we did illustrate very closely what it’s going to be like,” said Grasdal.

The restaurant is accepting reservations starting in April through September 2019, but has proven so popular that only waiting list spots are available. According to Grasdal, the best way to plan a visit is to look at the weather forecast. “I think the most exciting experience will be visiting the restaurant during rough weather,” he said.

“It will be fantastic to see the sea surface broken up by the big waves and the rain, making for a very dramatic view – although you will still feel safe and relaxed inside the restaurant.”