Crewed deep-sea submersibles have been around for decades
NOAA
The first comprehensive analysis of deep-sea dives has revealed that humans have only directly observed a tiny fraction – less than 0.001 per cent – of the global deep seafloor, leaving the vast majority of our planet unexplored.
Oceans make up 71 per cent of Earth’s total surface area, and around 93 per cent of that area is deep seafloor, classed as seabed deeper than 200 metres. While much of this ocean region has been mapped using satellites and ship-mounted sonar, very little has been directly observed.