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 10,928 metres to a point in the Pacific Ocean's Mariana Trench that is the deepest place on Earth. His dive went 16 metres lower than the previous deepest descent in the trench in 1960.

Vescovo found undiscovered species as he visited places no human had gone before. On one occasion he spent four hours on the floor of the trench, viewing sea life ranging from shrimp-like anthropods with long legs and antennae to translucent "sea pigs" similar to a sea cucumber.

He also saw angular metal or plastic objects, one with writing on it.

"It was very disappointing to see obvious human contamination of the deepest point in the ocean," Vescovo said in an interview.

Plastic waste has reached epidemic proportions in the world's oceans with an estimated 100 million tonnes dumped there to date, according to the United Nations. Scientists have found large amounts of micro plastic in the guts of deep-dwelling ocean mammals like whales.

Vescovo hoped his discovery of trash in the Mariana Trench would raise awareness about dumping in the oceans and pressure governments to better enforce existing regulations, or put new ones in place.

"It's not a big garbage collection pool, even though it's treated as such," Vescovo said of the worlds' oceans