Victor Vescovo, a retired naval officer, made the unsettling discovery as he descended nearly 10,928 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 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 man-made 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.

The object can be seen in video of the dive provided to Reuters by the Discovery Channel.

Plastic waste has reached epidemic proportions with an estimated 100 million tons 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 his 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. ‘Avatar’ and ‘Titanic’ filmmaker James Cameron was the last to visit in 2012 in his submarine, reaching a depth of 10,908 meters.

Prior to Cameron’s dive, the first-ever expedition to Challenger Deep was made by the U.S. Navy in 1960, reaching a depth of 10,912 meters.

‘It was an amazing experience,’ says Vescovo. ‘It was an amazing dive – I think almost exactly 12 hours – three and a half down, four on the bottom, I think the longest anybody’s ever been on the bottom of the Challenger Deep. And then about four hours up. I went through pretty much all of my electrical power and had to be swapping batteries around and circuits around. It was a great journey.’