Auckland company builds world's first seafloor restaurant

Mike Murphy, an aquarium technology specialist with MJ Murphy Ltd, in Auckland, adapted techniques similar to those seen in big public "walk-through" aquariums such as Kelly Tarlton's Auckland operation.

The initial concept plans for Kelly Tarlton's in 1985 were his first bid to design aquariums, but since then he has built them in Sydney, Perth, Queensland, Darwin, Hong Kong, Singapore, Kuala Lumpur, China, Thailand, Hawaii and Vanuatu.

He built the 9m by 5m wide restaurant - which opened earlier this year - between a lagoon and a coral reef offshore from Rangali Island in the Maldives. It was the brainchild of Ahmed Saleem, one of the owners of the Hilton's Maldives resort spread over two islands, Rangali and Rangalifinolhu.

The $US5 million ($NZ7.16 million) restaurant - named Ithaa (which means pearl in Dhivehi, the language of the Maldives) - consists of 3m sections of clear acrylic 125mm thick arches sitting 1m below the sea level during low tide and almost 2m at high tide.

Mr Murphy said that the arches - the widest so far constructed underwater - were sealed to each other and the structure with a special silicone sealant: "It's about twice the Kelly Tarlton's span".

The restaurant's timber structure was from treated NZ pine and it was lined inside with Canadian red cedar.

The entrance to the restaurant, on the surface, had a "freeboard" of nearly 1.5m, but Mr Murphy said the tsunami came close to swamping it and filling the room with water. He said it had been designed to cope with rises in sea levels over the next two decades expected to be caused by global warming.

Of the 86 other Maldives resorts, 32 were affected in varying degrees by the Boxing Day tsunami, and seven resorts remain closed.

The archipelago has 200 main islands and nearly 1000 small atolls and reefs. The sea-floor restaurant is part of a complex spread over two islands linked by a 500m footbridge on the South Ari Atoll, a 45-minute flight from the capital, Male.

The restaurant's total weight when it was lowered to the seabed was 175 tonnes, including 85 tonnes of sand placed in it to sink it into the sea.

"The sand sinks it, because all the air inside creates huge uplift," Mr Murphy said. "If they decide to re-paint it in 12 or 15 years time, they can just take out the sand ballast and it will float to the surface again".

Mr Murphy said the restaurant could have seated 30 or 40 people but the luxury resort set it up to take only 14 dinner guests at a time, at about $US170 a meal. The menu has a lot of seafood.

Though other restaurants have been built in Israel, Dubai and the Caribbean with views of giant aquariums, Ithaa offered the world's first aquarium-style undersea dining with the plastic "glass" giving panoramic underwater views.

He said the resort was planting a coral garden on the side of the restaurant that did not face the reef so that the rays, sharks and many colourful fish would swim on both sides of the restaurant.

During the day a diver does the job of a window cleaner.