The amount of plastic ending up in the ocean is set to treble in a decade without action to curb the problem, a major report has warned.
Plastics is one of a number of environmental issues facing the world's seas, along with rising sea levels and warming oceans, and metal and chemical pollution, the Foresight Future of the Sea Report for the Government said.
But there are also opportunities for the UK to cash in the global "ocean economy" - which is set to double to 3 trillion US dollars (£2 trillion) by 2030 - in areas where the country is a world leader, such as offshore wind.
The scientists behind the report warned of the danger of the oceans being "out of sight, out of mind", with more known about the surface of Mars and the Moon than the deep sea bed.
But it is hugely important to the UK, with 95% of the country's international trade travelling by sea, the internet carried by subsea cables, and oceans storing carbon dioxide and heat and producing oxygen and food.
There are major opportunities for robotics, artificial intelligence and automated technology to fill gaps in understanding of the oceans and how best to manage them, the experts said.
For example, the submarine Boaty McBoatface has recently completed an unmanned mission under Antarctica's ice shelf to assess whether the ice is melting from below due to warmer seas.
Satellite technology can prevent illegal fishing and autonomous underwater sensors can check if carbon dioxide is escaping from subsea carbon storage facilities.
Work is also beginning on the impacts of plastic in the ocean, as experts are not sure what threats it poses, Professor Ian Boyd, chief scientific adviser for the Environment Department said.
Plastic pollution, which is set to treble between 2015 and 2025 without intervention, has a physical presence in the oceans, and can accumulate on the coasts or in particular areas of the sea.
But the toxic effects when they break down and end up inside marine organisms are not clear, he said.
But he added: "Even in absence of research, there is a precautionary principle to take here, which is we should minimise the amount of plastic, both macro-plastic and micro-plastic, going into the marine environment, in order to make sure that if there are toxic effects, those are being dealt with."
Efforts to reduce plastic pollution should focus on preventing it entering the sea, introducing new biodegradable plastics and public awareness campaigns about marine protection.
Professor Ed Hill, executive director of the National Oceanography Centre, said it was time to change the attitude of what goes on below the surface as "out of sight, out of mind" and have more of a "Mission to Planet Ocean" approach.
He said: "When people get to see what is in the ocean, and the Blue Planet series and so on have helped people to visualise it, and then I think their reaction is twofold, one is complete wonder at what is there, and in other cases complete horror at what we're potentially doing to it.
"It's this sense of the unexplored world on our own planet, but also it's important to us, we know less about the bottom of the sea than the moon or Mars, but nothing lives on the moon or Mars, but things live in our ocean and they're vitally important to us."
The oceans could provide new medicines, minerals and energy, he said.
The report said international collaboration and long-term planning was needed to protect the environment and enable the UK to make the most of the maritime economy.