Deepwater submersibles have existed for decades
NOAA
The first comprehensive analysis of deep water dives has revealed that humans have only directly observed a small fraction that 0.001 percent or the bottom of the global deep background, leaving the vast majority of our planet without exploring.
The oceans constitute 71 percent of the total area of the Earth, and about 93 percent of that area is a deep seabed, classified as the deepest seabed of 200 meters. While much of this oceanic region has been mapping using satellites and sounding mounted on the ship, very little directly was observed.
]