Deep sea mining is the extraction of minerals from the ocean floor found at depths of 200 metres to 6,500 metres. Wikipedia

Mineral extraction from the ocean floor Wikidata

The most valuable of the marine mineral resources is petroleum. About 15% of the world's oil is produced offshore, and extraction capabilities are advancing. One of the largest environmental impacts of deep sea mining are discharged sediment plumes which disperse with ocean currents and thus may negatively influence the marine ecosystem. Coal deposits known as extensions of land deposits , are mined under the sea floor in Japan and England. OmegaWiki