Less Than 0.001 Percent of the Deep Seafloor Has Been Seen

The whole seafloor has been mapped, in a sense. NOAA Ocean Exploration explains that satellite data cover all of it, but only as a general picture in which features like seamounts and shipwrecks remain unseen. Detailed mapping is further behind. As of April 2026, 28.7 percent of the global seafloor had been mapped with modern high-resolution sonar, usually mounted on ships. Seeing it is another matter. In NOAA’s words, we cannot say we have explored the seafloor until we have seen it, and explorers have seen less than 0.001 percent of the deep ocean seafloor, roughly the size of Rhode Island. That leaves a great deal, because more than 90 percent of the ocean is deep ocean, deeper than 200 meters. NOAA adds a sober conclusion: the ocean will never be fully explored.