An American explorer has completed the deepest ocean dive in history – and discovered plastic waste littering the sea floor 6.8 miles down.

Victor Vescovo’s submarine descended 35,853ft (10,928m) to the bottom of the Pacific Ocean’s Mariana Trench, the most remote place in the seas.

The retired naval officer found undiscovered species including shrimp-like anthropods and translucent “sea pigs” during four hours exploring the sea bed.

He also saw manmade rubbish – including a plastic bag, sweet wrappers and angular metal objects - in a place no human had ever been before.

"It was very disappointing to see obvious human contamination of the deepest point in the ocean," Mr Vescovo said.

Manmade rubbish, top right, is seen on the floor of the Mariana Trench - the deepest point of the world's oceans (Reuters) (REUTERS)

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

Scientists have found large amounts of micro plastic in the guts of deep-dwelling ocean mammals such as whales.

Mr Vescovo hoped his unsettling discovery in the Mariana Trench would raise awareness about dumping waste in the oceans and pressure governments to strengthen or better enforce regulations.

"It's not a big garbage collection pool, even though it's treated as such," he said.

Plastic waste across the world: in pictures Show all 15 1 /15 Plastic waste across the world: in pictures Plastic waste across the world: in pictures A father and son on a makeshift boat made from styrofoam paddle through a garbage filled river as they collect plastic bottles that they can sell in junkshops in Manila. The father and son team earn some three US dollars a day retrieving recyclables from the river. AFP/Getty Plastic waste across the world: in pictures A composite image of items found on the shore of the Thames Estuary in Rainham, Kent. Tons of plastic and other waste lines areas along the Thames Estuary shoreline, an important feeding ground for wading birds and other marine wildlife. Getty Images Plastic waste across the world: in pictures Children collect plastic water bottles among the garbage washed ashore at the Manila Bay. According to the United Nations Environment Programme, at current rates of pollution, there will likely be more plastic in the sea than fish by 2050. AFP/Getty Plastic waste across the world: in pictures Plastics and other detritus line the shore of the Thames Estuary. In December 2017 Britain joined the other 193 UN countries and signed up to a resolution to help eliminate marine litter and microplastics in the sea. It is estimated that about eight million metric tons of plastic find their way into the world's oceans every year. Once in the Ocean plastic can take hundreds of years to degrade, all the while breaking down into smaller and smaller 'microplastics,' which can be consumed by marine animals, and find their way into the human food chain. Getty Plastic waste across the world: in pictures A dump site in Manila in 2013. The Philippines financial capital banned disposable plastic shopping bags and styrofoam food containers, as part of escalating efforts across the nation's capital to curb rubbish that exacerbates deadly flooding. AFP/Getty Images Plastic waste across the world: in pictures Children swims in the sea full of garbage in North Jakarta, Indonesia. Getty Plastic waste across the world: in pictures An Indian woman holds a jar filled with Yamuna river water polluted with froth and toxic foam to be used for rituals at the river bank in New Delhi, India. The Yamuna River, like all other holy rivers in India, has been massively polluted for decades now. The river that originates in a glacier in the pristine and unpolluted Himalayas, and flows through Haryana, Delhi and Uttar Pradesh before merging with the Ganges River in Allahabad, once used to be the lifeline of the Indian capital. Currently, it is no more than a large, open sewer that is choking with industrial and domestic discharge that includes plastic, flowers and debris and has virtually no aquatic life. EPA Plastic waste across the world: in pictures Plastic waste is washed up on South Troon beach in Scotland. Recent reports by scientists have confirmed, plastics dumped in the world oceans are reaching a dangerous level with micro plastic particles now being found inside filter feeding animals and amongst sand grains on our beaches. Getty Plastic waste across the world: in pictures Children collect plastic to be sold and recycled, in a polluted river in suburban Manila. The city's trash disposal agency traps solid waste floating down waterways that was thrown into the water by residents of slums along riverbanks upstream. AFP/Getty Plastic waste across the world: in pictures View of the Carpayo Beach in La Punta, Callao, some 15 km of Lima. In 2013, the NGO VIDA labeled the Carpayo Beach as the most polluted in the country - 40 tons of trash on each 500m2. AFP/Getty Plastic waste across the world: in pictures Trash from Kamilo Beach in Hawaii. Gabriella Levine/Flickr Plastic waste across the world: in pictures A scavenger collects plastic cups for recycling in a river covered with rubbish near Pluit dam in Jakarta. Reuters Plastic waste across the world: in pictures Rubbish fills Omoa beach in Honduras. Floating masses of garbage offshore from some of the Caribbean's pristine beaches are testimony to a vast and growing problem of plastic pollution heedlessly dumped in our oceans, locals, activists and experts say. AFP/Getty Plastic waste across the world: in pictures A man climbs down to a garbage filled river in Manila. Plastic rubbish will outweigh fish in the oceans by 2050 unless the world takes drastic action to recycle the material, a report warned in 2016. AFP/Getty Plastic waste across the world: in pictures Garbage on East Beach, Henderson Island (Pitcairn Islands), in the south Pacific Ocean. The uninhabited island has been found to have the world's highest density of waste plastic, with more than 3,500 additional pieces of litter washing ashore daily at just one of its beaches. EPA

Mr Vescovo, a Dallas-based private equity investor, has made four dives in the Mariana Trench in his $48m (£37m) private submarine, DSV Limiting Factor, over the past three weeks. He has biological and rock samples during the descents.

His latest expedition went 52ft (16m) lower than the previous deepest descent in the trench in 1960.

It is the third time humans have dived to the trench’s deepest area, known as Challenger Deep. Canadian film director James Cameron was the last to visit in 2012 in his submarine, which reached a depth of 35,787ft (10,908m).

The first expedition to Challenger Deep was made by the US Navy, which reached a depth of 10,912m in 1960.

News of Mr Vescovo's discovery came as Sir David Attenborough warned an "unfolding catastrophe" that we "ignore at our peril" was unfolded in Earth's oceans.

The wildlife expert said plastic in the sea was a "global problem" that demanded a response on an international scale.

The DSV Limiting Factor submarine has made four descents into the Mariana Trench (Reuters) (REUTERS)

Writing in the i newspaper, Sir David said it was "high time" for the world's leaders to take action on plastic pollution.

"I have seen for myself the effects of plastic pollution on some of our planet's most precious species and natural places - an unfolding catastrophe that has been overlooked for too long," he added.

Graphic: Statista

Scientists have previously found traces of fibres and plastics in the stomachs of creatures living in the Mariana Trench.