Under water sea pressure is ridiculous , Average folks don't realize the difficulty
Humans can't even go down and up unless they "Slowly depressurize"
For longest period the deepest zones of Ocean were never explore , even I hear we have only explored 12% of ocean under water world
But what is astonishing is , some life forms still exist at that great pressure level
When Titanic movie first came out most people imagined Humans can conquer the depths of ocean and pave way for research on Moon's with Solid ice , and perhaps a liquid ocean below
However judging that idea again , I don't think Humans are really anywhere close to mastering the Ocean