Space may be the final frontier, but here on Earth the ocean depths are one of the few places still shrouded in mystery. Though offshore drilling for oil and natural gas has gradually crept farther and farther from the coastlines since its advent in the late 1800s, many of the resources found beneath the world's salty waters remain relatively untouched. And although several countries, including Saudi Arabia and Sudan, have recently shown renewed interest in tapping these resources, the costs of operating in the difficult environment deep waters pose will likely preserve subsea basins for a little while longer. Mining the ocean floor first became popular in the 1960s, when claims of the "near-limitless" metals and minerals to be found there gave rise to a flurry of extraction projects. Those in shallow waters, including the search for diamonds off Africa's coast, saw some success.