The world’s largest underwater restaurant

Materials World magazine
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10 May 2019

Europe’s first subsea restaurant, Under,  has opened in Norway, offering an aquatic dining experience with a panoramic view.
 

An underwater restaurant has been submerged 5m-deep into the ocean in Lindesnes, the southernmost point of the coastline of Norway. The 495m2 construction is the world’s largest underwater restaurant, and is fully booked for the next six months with around 7,000 reservations.

Under, which means both below and wonder in Norwegian, is a 34m-long restaurant with the entrance on the shore before it breaks the water-surface to finally rest on the seabed. Diners will sit in front of an 11m-wide and 3.4m-tall window with a panoramic view of the sea life.

The Snøhetta-designed restaurant was built to integrate with its environment as time passes. Its concrete walls have been constructed with a rough surface to mimic a reef, providing a habitat for limpets and kelp. Before being submerged, the restaurant’s shell was built as a concrete tube with windows. Under was initially constructed on a barge before being guided to the final destination using a crane and tugboats. The edifice is bolted to a piece of concrete, anchored to the bedrock below the seabed. To ensure the bolts were securely fastened, the structure was filled with water, making it sink. When certain that all bolts were properly tightened, the water was drained and work on the interior could proceed. The restaurant’s panoramic window is acrylic and crafted, manufactured and installed by Reynolds Polymer Technology (RPT), Colorado, USA. The acrylic window measures 26.67cm-thick and is made of five custom cast pieces that were bonded together in the RPT facility, turning it into one seamless piece.

RPT used silicone sealant, as well as other installation materials, to not only waterproof the joints between the acrylic and structure, but also to allow the acrylic to move thermally. Reynolds Polymer Technology Vice President of Global Sales and Marketing, Mark Johnson, told Materials World the main elements to look out for when creating a window for underwater conditions are pressure and the dynamic loading of ocean waves, leading RPT to use finite element analysis to ensure the window would be able to withstand the pressure.

‘Unlike glass that must laminate thinner sheets together, RPT acrylic can be cast to the required thickness for the project in a single pour. This results in a material that has greater optical clarity and adaptability,’ Johnson said, adding that monolithic casting gives the desired clarity.

Under will also be used by research teams from different disciplines that study marine biology and fish behaviour. They will use cameras and measurement tools installed on the outside of the restaurant’s façade to study marine interactions. Norwegian Institute of Bioeconomic Research (NIBIO) researchers and other centres want to study how wild fish respond to sound signals and their behaviour through the changing seasons, as well as contributing to an environment for marine life to flourish.

The research has already made progress – NIBIO Marine Biologist Trond Rafoss has announced observing small European lobster larvae, normally only studied in laboratories and previously undetected in nature, through the restaurant’s window.