It is the third time humans have reached the ocean's extreme depths.
Victor Vescovo descended almost 11km (seven miles) to the deepest place in the ocean - the Pacific Ocean's Mariana Trench.
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.
Scientists plan to test the newly-discovered creatures to see if they contain microplastics. They also saw a spoon worm, a pink snailfish, and a colored rocky outcrops, all inhabitants of the deep sea.
First, Vescovo will dive to the second deepest trench in the Pacific, the Tonga Trench, he says there is a slim chance it could actually be deeper than the Mariana Trench.
"It's nearly indescribable how excited all of us are about achieving what we just did", Vescovo said.
Vescovo broke the previous Mariana Trench diving record by about 36 feet.
On May 1, Vescovo set a record for the deepest dive and deepest solo dive, using a titanium Triton submersible called Limiting Factor to descend 35,853 feet, the Five Deeps Expedition announced Monday morning. Atlantic Productions for Discovery Channel/Handout via REUTERS.
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.
"We feel like we have just created, validated, and opened a powerful door to discover and visit any place, any time, in the ocean - which is 90 percent unexplored".
The first deep dive into the Mariana Trench was in 1960, when U.S. Navy Lieutenant Don Walsh and Swiss engineer Jacques Piccard ventured into the deep abyss of the Pacific Ocean.
The dive forms part of the Five Deeps expedition - an attempt to explore the deepest points in each of the world's five oceans.
Canadian filmmaker James Cameron was the last to visit the location in 2012 in his submarine, when he reached a depth of 10,908 metres.
As well as the Mariana Trench in the Pacific, in the last six months dives have also taken place in the Puerto Rico Trench in the Atlantic Ocean (8,376m), the South Sandwich Trench in the Southern Ocean (7,433m) and the Java Trench in Indian Ocean (7,192m). The pressure at the bottom of the ocean is equal to about 50 jumbo jets piled on top of a person, according to BBC News.
His voyage, in a submersible named The Limiting Factor, is part of a landmark odyssey into the world's watery depths that's being filmed for Discovery Channel - dubbed the Five Deeps Expedition.
They also observed a variety of critters.