At the bottom of the ocean lies a treasure. But recovering it could be technically difficult, geopolitically challenging, and environmentally damaging.

Eighty three percent of the ocean is a mile deep, or much more, making the deep ocean the largest environment on Earth, covering 115 million square miles.

Down there, like in the Amazon, species diversity is high. There may be thousands of species we have not yet identified.

Down there, also, are polymetallic nodules and crusts, formed of iron and manganese, and in smaller amounts, cobalt, lithium, molybdenum, rare earth elements and other valuable metals that precipitate out of seawater, very slowly, over millions of years.

Many of these metals are used in new energy technologies, like batteries, so companies and countries are considering recovering them. But it’s complicated.

Most of the deep ocean is in international waters. No one’s quite sure how to regulate or share revenue from mining there.

And the deep ocean is a poorly understood environment. Mining could kill many creatures and damage seafloor ecosystems.

So far, no permits have been issued. But there is pressure on international authorities to do so, as today’s supplies of many of these materials are limited.

Efforts to mine the deep ocean, responsibly and sustainably, may be an area of dispute—and opportunity—in the future.