Retired Naval Officer Victor Vescovo dove nearly 36,000 feet in the Pacific Ocean’s Mariana Trench only to find what appears to be plastic waste.

According to The Guardian, Vescovo is still trying to confirm that the material he found is indeed plastic. Vescovo made the discovery during a 10,927-meter descent into the Mariana Trench, which is said to be the deepest place on Earth, noted the report.

Over the past three weeks, Vescovo’s expedition has made four dives in the Trench via submarine and has been collecting biological and rock samples. This is the third time humans have gone down to the deepest point in the ocean, according to the report.

The Guardian has more information:

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: litter.

Victor Vescovo, a retired naval officer, made the unsettling discovery as he descended nearly 35,853ft (10,927 meters) 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. His dive went 52ft (16 meters) lower than the previous deepest descent in the trench in 1960.

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 Stephanie Fitzherbert, a spokeswoman for Vescovo’s Five Deeps Expedition.

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