Beginning in early February, 100 million litres of water were drawn out of Sydney Harbor, exposing two hectares of the Blackwattle Bay seabed and a massive grid of steel pylons.

Using water pumped from the bay, a temporary cofferdam, or watertight building, was built to permit the safe construction of the NSW government's much-anticipated $750 million new Sydney Fish Market.

The largest cofferdam ever erected in NSW, according to Minister of Infrastructure, Cities, and Active Transportation Rob Stokes.

“This is a feat of engineering on steroids. There is so much complexity in what is being delivered,” Stokes said on Wednesday.

The idea to move the fish market from its current location in Pyrmont to the head of Blackwattle Bay in Glebe is progressing forwards.

In addition to building the future metro rail line, the government has ambitious plans to transform the largely industrial western harbour foreshore with more intensive development.

The cofferdam was constructed using more than 1000 interconnected sheet and tubular piles that have been driven into the bed of the bay. The enclosed construction has been drained to roughly four metres below sea level.

The cofferdam's "dewatering," according to Multiplex Regional Director Daniel Murphy, was accomplished in "a controlled manner while respecting the environment and the local ecosystem."

“It’s a significant structural challenge, and we have worked with experts across the globe to arrive at today’s destination,” he said.

According to Stokes, the new fish market would be supported by outdoor public areas, wharves, and a 15-meter wide seafront promenade. It would also contain restaurants, bars, and an expanded seafood cookery school.

He said the project would be executed on schedule and within its $750 million budget despite the cost to taxpayers of creating the new fish market skyrocketed by half a billion dollars in 2019. It must be finished by 2024.

Locals are nonetheless upset by "the huge blowout in cost for what is essentially a glorified shopping centre over Blackwattle Bay," according to Balmain MP Jamie Parker.

Stokes defended constructing over such a wide portion of the waterway, which is popular with rowers, and said the bay’s edge, which once housed a concrete batching plant, has been blocked off from the public for decades.

“We believe that it is worth doing to provide an iconic piece of architecture for future generations to enjoy,” he said.

“This is a real opportunity to ensure we used public space wisely and maximised the opportunity for people going to the fish market, but also to everyone else, to get an adornment to the public realm as well.”

The building, which had a fish-scale-inspired roof design, would be the "third iconic structure on the harbour after the Opera House and Harbour Bridge," according to Greg Dyer, chief executive of Sydney Fish Market.

The next stage of the project entails creating the concrete building with the underground parking.

To offset the expense of the new structure, the government is using money made from developing the location of the current fish market.

In response to significant opposition from communities over proposals for more intensive development, Infrastructure NSW last year unveiled a revised proposal to create 1200 flats in buildings up to 35 storeys on the current fish market site.

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