SANTA FE (REUTERS) - On the deepest dive ever made by a human inside a submarine, a Texas investor found something he could have found in the gutter of nearly any street in the world: trash.

Mr Victor Vescovo, a retired naval officer, made the unsettling discovery as he descended nearly 10,928m to a point in the Pacific Ocean's Mariana Trench that is the deepest place on Earth, his expedition said in a statement on Monday (May 13).

His dive went 16m lower than the previous deepest descent in the trench in 1960.

Mr Vescovo, the Dallas-based co-founder of Insight Equity Holdings, a private equity fund, found the manmade material on the ocean floor and is trying to confirm that it is plastic, said Ms Stephanie Fitzherbert, a spokesman for Mr Vescovo's Five Deeps Expedition.

Plastic waste has reached epidemic proportions, with an estimated 100 million tonnes of it now found in the world's oceans, according to the United Nations.

In the last three weeks, the expedition has made four dives in the Mariana Trench in Mr Vescovo's submarine, "DSV Limiting Factor", collecting biological and rock samples.

It was the third time humans have dived to the deepest point in the ocean, known as Challenger Deep. Canadian movie maker James Cameron was the last to visit in 2012 in his submarine, reaching a depth of 10,908m.

Prior to Mr Cameron's dive, the first-ever expedition to Challenger Deep was made by the US Navy in 1960, reaching a depth of 10,912m.