Very interesting! At that depth, the water pressure is 15,500 pounds per square inch! This means parts of the submarine structure not constructed of metal, such as glass (?) windows, (if there are any), must be super-strong. Likewise the sealing mechanisms in place to keep the water out. Inside, the air pressure is likely maintained at atmospheric, 14.7, or maybe a bit higher. I wonder about the water temperature? Cold water sinks......can't go any deeper than the Mariana! Frank "On the deepest dive ever made by a human inside a submarine, a Texas investor and explorer found something he could have found in the gutter of nearly any street in the world: trash. Victor Vescovo, a retired naval officer, said he made the unsettling discovery as he descended nearly 6.8 miles (35,853 feet/10,928 meters) to a point in the Pacific Ocean's Mariana Trench that is the deepest place on Earth. His dive went 52 feet (16 meters) lower than the previous deepest descent in the trench in 1960." See: https://www.yahoo.com/news/trash-found-littering-ocean-floor-deepest-ever-sub-202235416.html
The headline and commentary make it sound like the entire floor of the ocean were covered with trash, but the actual test of the article simply says, after talking about his having discovered new species, ...
@Ken Anderson After having seen the aerial photos of the "dead zones", in which nothing is said to be able to live, I can't help but begin to feel the oceans have been besmirched. Areas as large as some of our eastern states. Frank
After centuries of ships routinely dumping refuse into the oceans and cities along the ocean dumping their refuse into the ocean, I would be surprise if that wasn't the case, but that article doesn't demonstrate it.