Victor Vescovo descended in his watercraft to the to the lowest part of the ocean in the Pacific's Mariana Trench, marking only the third time humans have reached the sea's extreme depths.
The last visit to the bottom of Challenger Deep was made in 2012 by filmmaker and explorer James Cameron, who reached a depth of 10,908 meters on a dive in his submersible, the Deepsea Challenger. The expedition also filmed a weird creature called a spoon worm for the first time at hadal death (7,000 meters or 22,966 feet).
Vescovo said he wasn't surprised by the discovery, though, disappointed to see "human contamination" in the deep ocean. Previously, the deepest dive totaled over 10,912 metres and was carried out by U.S. Navy lieutenant Don Walsh and Swish engineer Jacques Piccard in 1960.
In addition to discovering at least three new species of marine animals during the dive series, including a shrimp-like crustacean known as an amphipod, the team also discovered what appears to be a plastic bag at the bottom of the ocean.
An object described by a spokesperson for the Five Deeps Mariana expedition as "manmade" is illuminated at top right by the light of the submarine DSV Limiting Factor on the floor of the Pacific Ocean's Mariana Trench, in an undated still image from video released by the Discovery Channel May 13, 2019.
The United Nations estimates 100 million tons of plastic waste already occupies the world's oceans and large volumes of microplastic have been discovered in the intestinal tracts of deep-dwelling ocean mammals, UK's Telegraph newspaper reported.
Vescovo made multiple trips through the trench.
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.
Mr Vescovo's latest dive is part of the "Five Deeps expedition", where he is attempting to explore the deepest parts of all five oceans.
As well as working under pressure, the sub has to operate in the pitch black and near freezing temperatures.
Before now, the Five Deeps Expedition surveyed the Puerto Rico Trench in the Atlantic Ocean, and the South Sandwich and Java Trenches in the Indian Ocean.
Anthony Geffen, creative director of Atlantic Productions, said it was the most complicated filming he'd ever been involved with. "I'm hopeful that we'll be able to study the ocean before we destroy it". The group is using a submersible called Limiting Factor to complete its challenge. There is also growing evidence that they are carbon sinks, playing a role in regulating the Earth's chemistry and climate.