Kiwis Against Seabed Mining is also appealing the marine consents granted to Trans-Tasman Resources to mine the South Taranaki seabed, and so is a fisheries collective that includes Talley's Group Ltd.
Other groups that may appeal include Forest and Bird and Te Ohu Kaimoana, and tribal groups Ngā Rauru, Ngā Ruahine and Whanganui iwi.
Each appellant will have to "bounce off" matters it has already raised in its submission to the Environmental Protection Authority. Mrs Ngarewa-Packer said Ngāti Ruanui's submission had four points of law it can raise in the High Court.
Its case is likely to draw on issues highlighted by the two commissioners who disagreed with granting consent, Sharron McGarry and Gerry Te Kapa Coates.
Ngāti Ruanui was ideally placed to appeal the consents because it had its own environmental unit with seasoned staff. Without that an appeal would be a tough process, Mrs Ngarewa-Packer said.
"I feel aroha for those fundamentally opposed but who are going to have trouble with some of the appeal detail."
In the midst of all this she's stoked that the Green Party has reacted by suggesting a marine sanctuary for those troubled waters.
"It's the only party bringing up other solutions."