Only about 0.001 percent, an area roughly the size of Rhode Island
A 2025 study in Science Advances estimated that in roughly 70 years of deep-sea diving, humans have visually observed only about 0.001% of the deep seafloor, an area about the size of Rhode Island. That leaves more than 99.999% never seen by human eyes. Most of the seafloor has only been mapped at coarse resolution by sonar and satellite-derived bathymetry, which reveals shape but not what actually lives there.
