If the ocean is the planet’s final frontier, the ocean floor is a frontier beyond that -- a lawless and often-overlooked space of vast mineral wealth and undiscovered biological diversity. Brazil requires an environmental impact assessment before allowing companies to drill or mine in its national waters. Scientists with Greenpeace set out to do their own assessment of plans to drill at the mouth of the Amazon River.

Ian Urbina traveled with them to understand a fight unfolding in this space. On one side was a trio of energy companies; on the other, a team of Brazilian scientists. The energy companies paid top dollar for the right to drill in a specific patch of sea floor. The Brazilian researchers hoped to stop them, claiming that the drilling there would jeopardize a 621-mile-long coral reef nearby.