The sea floor between Hawaii and Mexico is covered in potato-sized rocks that contain many of the metals necessary to make electric-car batteries. All that’s needed is a way to lift them to the surface for processing. At least, that’s the theory behind the Metals Co., a business formed earlier this year when the Canadian startup DeepGreen merged with a special-purpose acquisition company. As the company prepares to go public, it’s touting seabed mining as a green alternative to land-based mineral extraction — and potentially a hugely lucrative business.

Not everyone is quite so optimistic. Since June, 530 marine-science and policy experts from 44 countries have signed a statement warning that seabed mining would result in environmental damages “irreversible on multi-generational timescales.” That should alarm not just investors, but policy makers charged with protecting the oceans.