This map displays the 822 square miles of total observed deep seafloor overlaid on the Philadelphia region. Scientists estimate there are somewhere between 700,000–1 million species living in the approximately 139 million square miles of water. If you want to add those to your tally, you’ll need to tack on a few more million to the total number of species. According to NOAA, just 26.1 percent of Earth’s ocean floors have been mapped using high-resolution technology, as of June 2024. Meanwhile, only about 10 submersibles in the world are currently certified for deep ocean travel.