Underwater wonder

A bit of backyard engineering magic was behind one of Auckland’s best-loved tourist attractions, Kelly Tarlton’s Underwater World.  HUGH DE LACY unravels it.

Of course the Japanese were always going to say only they could bend transparent acrylic panels into half-circles to make a water-tight tunnel through which people could walk along the bottom of a giant aquarium. At the time – the early 1980s – they were, after all, the acknowledged leaders in acrylic panel technology.

Nor were they about to sell that technology cheaply to a self-styled marine archaeologist from New Zealand with a crazy dream of making the experience of underwater exploration available to the dry masses on dry land.

So rather than pay the big prices the Japanese demanded for curved panels, Kelly Tarlton bought 30-odd tonnes of flat see-through ones from Germany, and moulded them into shape himself back home in Auckland.

Before that there was no aquarium in the world that allowed people to walk among the fishes, and Tarlton’s became the standard by which all others are now judged.

Tarlton was already world-famous in New Zealand when he came up with his idea of a walk-through aquarium.

Born in Northland in 1937 but growing up in Christchurch, he had been a pioneer of what later became known as scuba diving.

He built his own diving gear, including a regulator and underwater cameras made out of old aircraft parts, before such gear was freely available in the leisure market.

While working for the Post Office, Tarlton established himself as an underwater construction diver before getting the sunken treasure bug and going after the likes of the gold believed to have gone down with the passenger steamer Elingamite when it slammed into the Three Kings Islands north of Auckland on a foggy night in 1902.

He later recovered a chest of jewellery, owned by a member of the Rothschild family, on the wreck of the Tasmania, another passenger steamer that sank off Hawke’s Bay’s Mahia Peninsula in 1897.

The Rothschild jewellery was the star attraction of a floating museum Tarlton then built at Paihia in the Bay of Islands on an old sugar lighter called the Tui.

And it was at Paihia that Tarlton first got his idea of a walk-through aquarium – in fact he would have built it there had he not run into local planning opposition.

So he found another site, an extraordinary one: a group of three huge disused underground sewage storage tanks at Orakei on the Auckland City foreshore, directly under Tamaki Drive which links the central city to Mission Bay.

The tanks, each 10 metres wide by 250 metres long and 2.7 metres high, lay alongside each other, parallel to the sea-wall.

Built around 1910 with their floors about a metre below mean sea-level so the sewage could be flushed out by the tides, the tanks had been used only as an emergency outlet since the city’s big new sewage treatment plant was established at Mangere in the 1960s.

Tarlton acquired the site and set about creating his aquarium in two of the tanks – the third would later be incorporated into the facilities as an education room and back-of-house service area.

The key to it all was the walk-through tunnel, and the key to that was bending the acrylic sheets, of which there were 31, each three metres long by 1500mm wide, either 55mm or 65mm thick and weighing a tonne.

Tarlton’s answer to the bending challenge was to make a concave mould out of 4x2s and insulation batts, set inside a kiln that was like a tiny room.

The acrylic panels were sat one by one on the top of the mould and then, as the kiln was heated by gas to around 100˚C – not hot enough for the timber to catch fire – they would soften and sag into the bottom of the mould.

Over the next 24 hours or so the heat would be slowly reduced and the acrylic would settle into its final curved shape.

From there it was a simple enough operation to line the curved panels up and seal them together on their concrete base to form a 110 metre, figure-eight tunnel.

Garry McMurtrie, who’s been maintenance manager at what is now Kelly Tarlton’s Underwater World for the past 22 years, told Contractor Tarlton got the bending formula right virtually from the start, though he slightly over-cooked the first panel and McMurtrie can today point out the small flaw in its surface that resulted.

“The Japanese said it couldn’t be done outside of Japan, but Kelly proved them wrong,” McMurtrie says.

The Underwater World with its novel feature of a conveyor belt that carried people along the tunnel, opened in January, 1985, to a startling public response that saw Tarlton welcoming the 100,000th visitor within just two months.

Soon after, Tarlton died of heart complications which may have been related to the long hours he’d spent on an aqualung, but the attraction he created continued to flourish and expand.

In 1987 the third sewage tank was incorporated into the business, and in 1994 a 2400 square metre Antarctic Encounter was added, offering visitors a stroll through a re-creation of Robert Falcon Scott’s 1912 expedition hut, followed by a Snowcat ride among colonies of king and gentoo penguins.

In 2004 a further refinement, designed by Auckland engineering firm Thorburn Consultants, was the 350,000 litre Stingray Bay, an open-topped acrylic tank containing two species of stingray and several kinds of school fish.

At the same time the original filtration system was replaced, and later a NIWA Interactive Room was installed to educate children about the marine world, and a series of smaller aquaria were built to display everything from red-bellied piranha to moray eels.

Almost the entire attraction is underground, with just the entranceway and carpark on the surface adjacent to the road.

The Tarlton family has long since relinquished ownership of the facility, selling first to Argus Questar which went bust. It was taken over by Tourism Holdings which in 2008 flicked it on to Village Roadshow, and in 2011, a year after celebrating its 25th anniversary, it was on-sold to the Merlin Entertainments Group.

Kelly Tarlton’s Underwater World remains today one of Auckland’s premier tourist attractions and a living monument to the man who foresaw the eagerness of people for an underwater attraction that allowed them to all but mingle with sea-life without getting wet.

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