The sea below 200 meters depth accounts for 95% of the volume of the ocean, making it the largest habitat for life on Earth. Though it is perpetually cold, generally dark, and subject to extreme pressures, the deep sea contains a wealth of unique and unusual species, habitats and ecosystems. It also contains a wealth of mineral resources, some of them in unique or highly enriched concentrations. Attempts to recover these resources during the 1970s and 1980s were impaired by legal uncertainties and technical constraints, along with metal prices that did not justify the enormous investments required. Today, the legal uncertainties have been largely resolved, marine mining and environmental monitoring technology has advanced rapidly. This report aims to stimulate interest in the deep ocean and the discussions surrounding its potential development, with a specific focus on deep-sea mining of hard metal-bearing minerals.