Trans-Tasman Resources' integrated mining vessel would be tethered by four anchors, have a crew of 140, a helipad and operate 24/7.
South Taranaki is an international trailblazer when it comes to seabed mining.
"The mining industry is a massive train rolling toward the oceans to mine the seabed," says Phil McCabe, chairman of Kiwis Against Seabed Mining (KASM),
"There's so much momentum that it's frightening - and here we are in New Zealand, leading the way."
Mr McCabe was speaking in the wake of last week's approval for Trans-Tasman Resources to mine ironsand from the South Taranaki Bight off the coast of Patea.
His KASM group was one of those opposing the controversial application. He said more mining would follow if the TTR venture was successful.
The approval by the Environmental Protection Authority has encouraged Chatham Rock Phosphate to make a second application to mine off the east coast of the South Island.
It could be easier to get consent this time, because of a recent amendment to EEZ law.
"Now the minister gets to appoint the decision-making committee," Mr McCabe said.
TTR has other pieces of seabed in its sights, including two next to the 66sq km area in its application, and another off Kawhia. It also has plans for a stretch off the South Island's West Coast, where there are ilmenite, garnet, gold, zircon and rutile.
It could be harder to get consent to mine closer inshore because that will be covered by the Resource Management Act rather than the EEZ legislation.
Other companies are also sniffing around. Ironsands Offshore Mining has a prospecting permit off the coast of New Plymouth, and Pacific Offshore Mining has one for seabed off Waihi Beach.
In March, the New Zealand Herald reported a "gold rush mentality" as companies saw opportunities to mine the rare metals used in solar cells, rechargeable batteries and wind turbines off the seabed. They're getting harder to find and extract on land.
In the Pacific Ring of Fire there are places where rare and precious metals are exuded from underwater vents as nodules, crusts and part of sulphide deposits.
Off Papua New Guinea, Canadian company Nautilus Minerals is preparing to use huge robot machines to scrape copper and gold off the seafloor at a depth of 1600m.
According to Wikipedia, both Nautilus Minerals and Neptune Minerals would like to mine the offshore waters of New Zealand.
Trans-Tasman Resources' consent can be appealed until August 31. Kiwis Against Seabed Mining (KASM), two Taranaki iwi and Forest & Bird are likely to appeal, either separately or together.
KASM chairman Phil McCabe said there has been a "phenomenal" response to its appeal for funds to take the fight to the High Court, with money coming in from Europe, the United States and Australia as well as New Zealand.
Meanwhile, South Taranaki iwi Ngā Rauru has asked the Taranaki/Whanganui Conservation Board to get a legal opinion on whether the board has grounds for an appeal.